Watch Construction & Anatomy
Every watch is built from the same handful of parts -- a case to hold the movement, a crystal and dial to read the time through, hands to point the way, and lugs, a band and a clasp to fix it to your wrist. This hub is the anatomy of a watch, part by part, grouped into three areas: the case & bezel, the dial side, and the lugs, bands & clasps that carry it. Each part is explained in plain English -- what it is, how it works and why it matters -- so you can read any spec sheet with confidence. For how the parts are measured to fit your wrist, see our watch measurements guide; for the metals they are made from, the watch materials hub.
Anatomy of a watch at a glance
| Part | Where it is | What it does |
|---|---|---|
| Case | The whole body | Holds and protects the movement, dial and hands |
| Bezel | Ring at the front | Frames the crystal; may rotate to time or read speed |
| Crown | Side of the case | Winds the watch and sets time and date; seals the case |
| Crystal | Over the dial | Clear, scratch-resistant window onto the dial |
| Dial | Behind the hands | The face you read the time against |
| Hands | Centre of the dial | Point to the hours, minutes and seconds |
| Caseback | Rear of the case | Seals in the movement; may display it |
| Lugs | Corners of the case | Attach the strap or bracelet via spring bars |
| Bracelet / strap | Around the wrist | Secures the watch; sets much of its character |
| Clasp | Ends of the band | Fastens the band and keeps the watch on |
Case & Bezel
Case
The body of the watch -- the metal shell that holds the movement, dial and hands and protects them from water, dust and knocks. Everything else is fixed to it.
What it is
The case is the central structure of a watch: the shell that houses and protects the movement, with the dial and hands sealed behind the crystal at the front and the caseback closing it at the rear. Its shape -- round, cushion, tonneau or square -- and its size in millimetres set the whole character of the watch. Most of ours are stainless steel or titanium; the metals are covered in full on our watch materials hub.
How it is built
A conventional case is made in parts: a middle (the main band that carries the lugs and crown tube), a bezel ring at the front holding the crystal, and a caseback at the rear. Gaskets sit between each joint to keep water out. The fewer the openings and the better the seals, the higher the water resistance the case can achieve.
Monocoque and one-piece cases
Some tougher watches use a monocoque (one-piece) case, where the middle and caseback are a single block of metal with no rear opening at all -- the movement is fitted from the front, under the crystal. With one less joint to seal, a monocoque case resists water and dust especially well, though servicing means going in through the dial side. Monocoque construction is shown here for understanding; most of our watches use a conventional removable caseback.
Why it matters
Case size, depth and shape decide how a watch wears, and the quality of its joints and gaskets decides how well it survives daily life. For how case diameter, thickness and lug-to-lug translate to fit on your wrist, see our watch measurements guide.
Bezel
The ring around the crystal at the front of the case. It can be a plain fixed frame or a working tool -- rotating, timing, tachymeter or dive -- depending on the watch.
What it is
The bezel is the ring that surrounds the watch crystal and holds it in place against the case. On a dress watch it is usually a slim, fixed, polished frame; on a sports or tool watch it becomes a functional instrument with markings and, often, the ability to turn.
Fixed, rotating and dive bezels
A fixed bezel is purely structural and decorative. A rotating bezel turns to perform a job: a dive bezel is unidirectional -- it only turns anticlockwise so an accidental knock can never make your remaining dive time read longer than it is -- and you line its zero marker up with the minute hand to track elapsed time underwater. A bidirectional bezel turns both ways for simpler timing or a second time zone.
Tachymeter and count-up bezels
A tachymeter bezel carries a fixed scale that converts elapsed seconds into a speed over a known distance -- pair it with a chronograph to read average speed. A count-up bezel marks 60 minutes for timing anything from parking to cooking. The bezel's job is closely tied to a watch's complications, covered in the complications hub.
In our range
Tissot and Citizen sports models -- such as the Tissot Seastar and the Citizen Promaster -- use working rotating bezels; most BOSS, Tommy Hilfiger and dress pieces use a clean fixed bezel. Browse Tissot watches for both styles.
Crown
The small grooved knob on the side of the case used to wind the watch and set the time and date. On water-resistant watches it screws down to seal the case.
What it is
The crown is the knob -- usually at the 3 o'clock position -- that you pull, turn and push to operate the watch. Pulled out to its first or second click it sets the date or the time; pushed home and turned (on a mechanical watch) it winds the mainspring. It connects to the movement through a tube fixed in the case, sealed with a gasket.
Screw-down crowns and water resistance
Because the crown has to move, it is the most likely place for water to get in. A screw-down crown solves this: it threads down onto the case tube and compresses a gasket to seal the watch shut, which is what lets a watch reach 100m / 10 ATM and beyond. You unscrew it to wind or set, then screw it fully home before any contact with water -- an open crown defeats the seal entirely. A simpler push-pull crown is fine for everyday splash resistance but not for swimming. The depth ratings are explained on our water resistance guide.
Pushers nearby
On a chronograph, two pushers sit above and below the crown -- the top one starts and stops the stopwatch, the lower one resets it. On sealed dive chronographs these can be screw-down too. Some watches also hide a recessed corrector button in the case side for setting calendars. Pushers are a chronograph feature -- see the complications hub for how the stopwatch works.
In our range
Tissot and Citizen sports and dive models use screw-down crowns for genuine water resistance; everyday quartz dress watches typically use a neat push-pull crown. See Tissot and Citizen watches.
Caseback
The back of the case, sealing in the movement. It can be solid, a screwed-in pressure seal, or an exhibition window that shows the movement off.
What it is
The caseback is the rear cover of the watch, closing the case behind the movement. It carries the engravings -- model and serial numbers, water-resistance rating and material -- and sits against your wrist, so its finish and shape affect comfort as well as sealing.
Solid, screw-down and exhibition
A solid caseback is a plain metal cover, the most robust and water-tight option. A screw-down (screw-in) caseback threads into the case middle against a gasket for high water resistance, and needs a special tool to open. A snap-on caseback presses into place and is quicker to service but seals less firmly. An exhibition (display) caseback replaces the metal with a sapphire or mineral window so you can watch the movement -- and, on an automatic, the rotor -- working away. It is a hallmark of a mechanical watch worth showing off; pure quartz watches almost always use a solid back.
Why it matters
The caseback choice trades visibility against toughness and water resistance: a sealed solid or screw-down back protects best, while an exhibition back is for admiring the calibre. To understand what you are looking at through a display back, see the movements hub.
Dial Side
Crystal
The clear cover over the dial -- the watch's window. Three materials dominate: acrylic, mineral glass and sapphire, in rising order of scratch resistance.
What it is
The crystal is the transparent disc that protects the dial and hands while letting you read the time. Despite the name it is rarely natural crystal -- the term covers acrylic plastic, hardened mineral glass and synthetic sapphire. It is the surface your watch knocks against most, so its hardness largely decides how the watch ages cosmetically.
Acrylic, mineral and sapphire
Acrylic (Plexiglas) is a light plastic crystal -- shatterproof and cheap, and light scuffs can be polished out, but it scratches easily. Mineral glass is hardened glass at around 5 to 6 on the Mohs hardness scale -- more scratch-resistant than acrylic and inexpensive to replace. Sapphire crystal is synthetic sapphire at 9 on the Mohs scale, second only to diamond, so it resists the keys, coins and desk knocks that mark softer covers. Sapphire is the quality standard and is often given an anti-reflective coating on its underside for glare-free legibility. The full comparison lives on our canonical sapphire crystal guide.
In our range
Tissot and Citizen use sapphire crystals across their watches, and many fashion pieces from BOSS and Tommy Hilfiger use hardened mineral glass. For the depth on scratch resistance and how to remove light marks, see the watch performance hub.
Dial
The face of the watch -- the backdrop carrying the hour markers, any text and sub-dials, that you read the time against. Also called the face.
What it is
The dial is the visible face of the watch, the plate behind the hands that displays the hour markers (indices), the brand name, and any sub-dials or date window. Its colour, texture and layout define the watch's looks more than any other single element -- from a clean sunburst dress dial to a busy, high-contrast sports dial.
Indices, chapter ring and rehaut
The markers around the dial are the indices -- applied metal batons, printed numerals or Roman numerals. The chapter ring is the narrow ring just inside the dial's edge that carries the minute or seconds track. The rehaut (or flange) is the angled inner ring between the dial and the crystal, which often carries the minute markings and, on some watches, engraved text. Together these fix exactly where the hands point, so their printing has to align precisely with the hands.
Sub-dials, windows and finishes
A sub-dial is a small dial-within-the-dial -- used for running seconds, a chronograph's elapsed time, or a day or 24-hour display. A date window (aperture) shows the date through a cut-out. Dial finishes range from sunray brushing and matte to guilloche engine-turning and lacquer. The functions these displays serve are covered in the complications hub.
In our range
Olivia Burton and Vivienne Westwood are known for decorative, characterful dials, while Tissot and Citizen run from clean dress faces to legible sports dials. Browse Olivia Burton and Tissot watches to compare.
Hands
The pointers that sweep the dial to show the hours, minutes and seconds. Their shape is a key part of a watch's identity, and many carry luminous fill.
What it is
The hands are the moving pointers fixed to the centre of the dial -- typically an hour hand, a longer minute hand and a thin seconds hand, plus extra hands on sub-dials for complications. They are mounted on concentric arbors driven by the movement, and must be perfectly fitted so they sweep cleanly without catching the dial or each other.
Hand styles
Hand shape is a signature of watch design. Common styles include the slim, pointed dauphine of dress watches; the bold, luminous sword and baton hands of sports watches; the rounded-tip Mercedes hand; the open-circle snowflake; and the elegant leaf (feuille). The seconds hand is often the lightest, sometimes with a counterweight tail or a coloured tip for a pop of contrast.
Lume on the hands
Sports and tool-watch hands are usually filled or coated with luminescent material -- modern Super-LumiNova -- so they glow in the dark after charging from light. Matching the lume on the hands to the markers keeps the time readable at a glance at night. The lume itself is covered in the watch performance hub.
Lugs, Bands & Clasps
Lugs
The horns projecting from the case that the strap or bracelet attaches to. They hold the band with spring bars and largely set how a watch sits on the wrist.
What it is
The lugs are the four arms -- two top, two bottom -- that extend from the case to hold the strap or bracelet. The strap is held between each pair of lugs by a spring bar, a tiny sprung pin that compresses to slot into drilled holes in the lug tips and springs out to lock the band in place. The reach of the lugs, measured tip to tip, is the lug-to-lug distance that decides whether a watch overhangs a smaller wrist.
End links and the bracelet fit
On a metal bracelet, the first link at each end -- the end link -- is shaped to curve neatly between the lugs and follow the case profile, giving a seamless, integrated look. A well-fitted end link sits flush with no gaps. On a strap, a fitted (curved) end achieves the same, while a straight strap simply passes between the lugs.
Spring bars and changing straps
Spring bars let you change a strap yourself: a spring-bar tool compresses the bar to release the band, and a fresh strap clicks straight in -- provided it matches the gap between the lugs. That gap is the lug width, which governs which straps will fit. Quick-release spring bars add a small lever so you can swap straps with no tool at all.
Why it matters
Lug shape, length and width determine both how a watch wears and which bands fit it. For how lug-to-lug and case size translate to your wrist, see the watch measurements guide.
Lug Width
The gap between the lugs in millimetres -- the single measurement that decides which straps will fit your watch. Common sizes are 18mm, 20mm and 22mm.
What it is
Lug width is the distance, in millimetres, between the inner faces of each pair of lugs -- the space the strap or bracelet end has to fill. It is almost always an even number: 18mm, 20mm and 22mm are the most common, with 16mm on smaller ladies' watches and up to 24mm on large sports models. A 20mm watch needs a 20mm strap; the next size up or down will not sit correctly.
How to find it
If it is not in the watch's specs, measure the gap between the lugs with a ruler or callipers. Strap sizes are quoted as the lug-width end first -- a strap listed as 20/18 is 20mm at the lugs and tapers to 18mm at the buckle. Getting the first number right is what matters for fit.
Why it matters
Lug width is the number to know before buying any replacement strap -- it governs strap fit completely. It sits alongside case diameter, thickness and lug-to-lug as the core watch measurements; the full set, with how to size a bracelet, is on our watch measurements guide.
Bracelet
A band made of linked metal that matches the case. Several classic link patterns exist -- Oyster, Jubilee, Milanese mesh and H-link among them.
What it is
A bracelet is a metal band built from interlocking links, usually in the same metal and finish as the case for an integrated look. It is sized by adding or removing links to fit the wrist, and fastens with a clasp. A good bracelet drapes smoothly, sits flush at the end links, and balances the weight of the watch.
Link styles
The Oyster is a sturdy three-piece flat link -- broad, sporty and robust. The Jubilee uses five smaller links per row, three polished in the centre, for a dressier, more flexible feel. Milanese (mesh) is a fine woven metal band that is smooth and supple with infinitely fine adjustment. An H-link (sometimes called a President or ladder link) uses an H-shaped central link for a refined, structured look. Beads-of-rice and engineer styles add further variety.
Sizing and comfort
Bracelets are adjusted by removing links at a watchmaker or at home with a link-removal tool, and many clasps add micro-adjustment holes for fine-tuning as your wrist changes through the day. To size one correctly, see the bracelet-sizing section of our watch measurements guide.
In our range
Steel bracelets feature across our Tissot, Citizen, BOSS and Vivienne Westwood watches, in polished, brushed and two-tone finishes. Browse Tissot, BOSS and Vivienne Westwood steel watches.
Strap
A band made of leather, rubber, NATO fabric or silicone, fastened with a buckle or clasp. Straps are the easiest way to change a watch's character.
What it is
A strap is a flexible, two-piece band -- as opposed to a one-piece bracelet -- that attaches to the lugs and fastens around the wrist. The material sets the mood: leather for dressy and classic, rubber or silicone for sporty and water-friendly, fabric NATO for casual and tough. Because straps fit by lug width, swapping one transforms the look of a watch in minutes.
Strap materials
Leather is the traditional dress strap -- supple, smart and available in countless finishes -- but it dislikes water and perspiration over time. Rubber and silicone are soft, hard-wearing and fully water-resistant, ideal for sports and dive watches. A NATO is a single nylon strap that passes under the caseback so the watch cannot fall even if a spring bar fails -- rugged and endlessly interchangeable. Sailcloth and textile straps blend a fabric look with water tolerance.
Hirsch straps at OD's
OD's stocks genuine Hirsch watch straps -- the long-established Austrian strap maker -- so you can re-strap or refresh a watch in store. With 9 Hirsch straps currently in stock across leather and water-resistant styles, it is an easy way to change a watch's look or replace a worn band. Match the strap's lug-width number to your watch -- see the watch measurements guide -- and our team can fit it for you.
Caring for a strap
Leather lasts longest kept away from water and rotated with other straps; rubber and silicone simply rinse clean. A quick-release spring bar makes tool-free swaps effortless, so one watch can wear several looks.
Clasp
The fastening that closes a strap or bracelet. From a simple pin buckle to a folding deployment clasp, it secures the watch and affects comfort and safety.
What it is
The clasp is the mechanism that fastens the band around your wrist. The choice ranges from the simple and slim to the secure and convenient, and it affects how easily the watch goes on, how safely it stays on, and how it feels against the skin. A good clasp clicks shut positively and holds firm.
Pin buckle, deployment and butterfly
A pin buckle (tang buckle) is the classic strap fastening -- a frame and pin through a hole, exactly like a belt -- slim, light and easy, but the strap bends fully open each time. A deployment (folding) clasp hinges open and closed in fixed sections so the strap or bracelet forms a loop that just slips over the hand, keeping the band's diameter constant and protecting a leather strap from creasing. A butterfly (double-fold) deployment clasp opens from both sides to the centre and tucks completely out of sight, leaving a clean, unbroken band -- a favourite on dress watches.
Safety and adjustment
Sports and dive clasps add a flip-lock or push-button safety catch so the clasp cannot pop open accidentally, plus micro-adjustment or a dive extension to fit over a wetsuit. A fold-over clasp with a safety latch is common on metal bracelets. Many clasps include several micro-adjust holes to fine-tune the fit as your wrist changes through the day.
In our range
Our bracelet watches use secure fold-over deployment clasps; strap watches come with pin buckles or deployment clasps depending on the model. To size the band the clasp closes on, see the watch measurements guide.
Frequently asked questions
What are the main parts of a watch?
The core parts are the case (the body), the bezel (the ring around the crystal), the crown (the winding and setting knob), the crystal (the clear cover), the dial (the face), the hands, the caseback (the rear cover), the lugs (which hold the band), and the bracelet or strap with its clasp. The movement -- the engine -- sits sealed inside the case.
What is the difference between a strap and a bracelet?
A strap is a flexible two-piece band, usually leather, rubber, fabric or silicone, that fastens around the wrist. A bracelet is made of linked metal that matches the case and is sized by adding or removing links. Both attach to the lugs, but a strap is the easiest way to change a watch's look.
What is lug width and why does it matter?
Lug width is the gap between the lugs in millimetres -- commonly 18mm, 20mm or 22mm -- and it decides which straps will fit your watch. A 20mm watch needs a 20mm strap; the wrong size will not sit correctly. It is the first number to know before buying any replacement strap.
What does the crown on a watch do?
The crown is the small knob on the side of the case. You pull it out to set the time and date, and on a mechanical watch you turn it pushed-in to wind the mainspring. On water-resistant watches it screws down against a gasket to seal the case shut.
What is a screw-down crown?
A screw-down crown threads onto the case tube and compresses a gasket to seal the watch, which is what allows water resistance of 100m / 10 ATM and above. You unscrew it to wind or set the watch, then screw it fully home before any contact with water -- an open crown lets water straight into the movement.
What is an exhibition caseback?
An exhibition (display) caseback replaces the solid metal rear cover with a sapphire or mineral window, so you can see the movement -- and the spinning rotor on an automatic -- working. It is common on mechanical watches worth showing off, and rare on pure quartz watches, which usually have a solid back.
What is the chapter ring on a watch?
The chapter ring is the narrow ring just inside the edge of the dial that carries the minute or seconds track. It works with the rehaut -- the angled inner ring between dial and crystal -- to fix exactly where the hands point, so the printing must align precisely with the hands.
What is a rehaut?
The rehaut (or flange) is the slanted inner ring between the dial and the crystal. It often carries the minute markings and, on some watches, engraved text such as the brand name. It frames the dial and adds depth to the face.
What is a bezel and does it always rotate?
The bezel is the ring around the crystal at the front of the case. It does not always rotate -- on a dress watch it is a fixed, decorative frame. On sports and dive watches it rotates to time events, with a dive bezel turning one way only so your timing can never read longer than it is.
What is the difference between Oyster and Jubilee bracelets?
An Oyster bracelet uses broad three-piece flat links for a sturdy, sporty feel. A Jubilee uses five smaller links per row, three polished in the centre, for a dressier, more flexible and supple feel. Both are classic steel-bracelet patterns.
What is a Milanese strap?
A Milanese (mesh) strap is a band of fine woven metal -- smooth, supple and elegant, with infinitely fine adjustment via a sliding clasp. It suits dressier watches and sits very comfortably as it has no rigid links.
What is a deployment clasp?
A deployment (folding) clasp hinges open and closed in fixed sections, so a strap or bracelet forms a loop that slips over your hand without bending fully open each time. It keeps the band's diameter constant and protects a leather strap from creasing, and is more secure than a simple pin buckle.
What is the difference between a deployment clasp and a butterfly clasp?
A standard deployment clasp folds from one side. A butterfly (double-fold) clasp opens from both sides towards the centre and tucks completely out of sight when closed, leaving a clean, unbroken band -- a favourite on dress watches.
What is a pin buckle?
A pin buckle (tang buckle) is the simplest strap fastening -- a frame and a pin that goes through a hole in the strap, exactly like a belt. It is slim, light and easy to use, though the strap bends fully open each time you take the watch off.
How do I change a watch strap?
Straps attach to the lugs with spring bars -- small sprung pins. A spring-bar tool compresses the bar to release the strap, and a new one matching your lug width clicks straight in. Quick-release spring bars add a small lever so you can swap straps with no tool at all.
Does OD's sell replacement watch straps?
Yes. OD's stocks genuine Hirsch watch straps -- the established Austrian strap maker -- with 9 currently in stock across leather and water-resistant styles. Match the strap's lug-width number to your watch and our team can fit it for you in store.
What is the crystal on a watch made of?
The crystal -- the clear cover over the dial -- is usually one of three materials: acrylic plastic (cheap, shatterproof, scratches easily), mineral glass (harder, around 5 to 6 on the Mohs scale), or synthetic sapphire (9 on the Mohs scale, the most scratch-resistant). Sapphire is the quality standard.
Is sapphire crystal better than mineral glass?
For scratch resistance, yes. Sapphire crystal sits at 9 on the Mohs hardness scale, second only to diamond, so it resists everyday scratches far better than mineral glass at around 5 to 6. Mineral glass is cheaper to replace, however. See our sapphire crystal guide for the full comparison.
What are the lugs on a watch?
The lugs are the four horns that project from the case and hold the strap or bracelet, secured by spring bars. Their length, tip to tip, is the lug-to-lug measurement that decides whether a watch overhangs a smaller wrist.
What are end links on a bracelet?
End links are the first links at each end of a metal bracelet, shaped to curve neatly between the lugs and follow the case profile for a seamless, integrated look. A well-fitted end link sits flush against the case with no gaps.
Why does my watch face reflect so much?
Glare comes from light bouncing off the crystal. Better watches add an anti-reflective (AR) coating -- usually on the underside of a sapphire crystal -- which lets more light through and reflects less back, so the dial stays readable in bright conditions.