A folding clasp, also called a deployant or butterfly clasp, is initially confusing for first-time users. It opens and closes differently from a standard tang buckle, and it must be correctly sized to your wrist before it functions well. Sizing the clasp correctly is part of every deployant commission. This guide walks through the mechanics, how to size it, and how to put it on and take it off.
Before You Start: Understanding the Three Positions
A butterfly clasp has three states:
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Fully closed (on the wrist): Both wings folded flat against the wrist. The clasp clicks shut and sits flush. This is the wearing position.
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Half open: The outer wing is open, folding away from the wrist. The inner fold and the strap attachment are still closed. This is the position for fitting around the wrist.
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Fully open: Both wings folded outward. The strap lies flat on a surface, used for cleaning, storage, or adjusting the clasp size.
Getting Sized (First Time Only)
A deployant clasp must be sized to your wrist before daily use. This is a one-time adjustment, typically done by a watchmaker or jeweller. Here's what the process involves:
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Put the watch on as if wearing it, with the clasp in the half-open position — outer wing open, inner fold closed, wrapped around your wrist.
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Fold the outer wing shut. It should click closed with the strap sitting comfortably on the wrist, not too tight, not too loose.
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If the clasp is too tight: the fold position of the clasp arm must be adjusted outward (toward the tip of the strap). If too loose: adjusted inward (toward the watch case).
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Most butterfly clasps have screws or push-buttons that allow the fold position to move along the strap in increments. A jeweller can adjust this quickly.
Do not force a butterfly clasp shut if it requires significant pressure. Forcing indicates the sizing is wrong, not that the clasp is defective. Have it adjusted.
Putting the Watch On
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Hold the watch face-up in your dominant hand with the clasp in the half-open position (outer wing open, inner fold closed around the strap).
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Slip the strap over your wrist. The watch case should sit at the 12 o'clock position; the clasp opens on the underside of the wrist.
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Fold the outer wing down toward your wrist. When it reaches the correct position it will click shut, a clean, firm click indicates the clasp is correctly seated.
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Run a finger along the clasp to confirm both sides are closed. Some clasps have bilateral release buttons, check both sides are engaged.
Taking the Watch Off
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Locate the release mechanism, typically two push-buttons or levers on both sides of the clasp (one on each wing).
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Press both buttons simultaneously. This disengages the lock and allows the outer wing to open.
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Open the outer wing. The clasp is now in the half-open position with the watch still around your wrist.
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Slide the watch off your wrist. The inner fold remains closed and the strap stays in its assembled position.
Frequently Asked Questions
Q. My butterfly clasp clicks shut but feels loose on my wrist. What is wrong?
The clasp fold position is set too far out from the watch case. The clasp closes at the correct click point, but there's too much slack in the strap before it reaches that point. Have the fold position adjusted inward (toward the case) by a jeweller.
Q. The outer wing will not click shut. It falls back open.
Either the sizing is wrong (too much resistance before the click point) or the clasp spring mechanism is worn or damaged. Try having the fold position adjusted first; if the clasp still won't hold, the locking spring may need replacement.
Q. Can I adjust the clasp size myself?
Some simpler clasps allow adjustment by repositioning a screw along a slot in the strap arm. Others require a watchmaker's tools. If unsure, take it to a jeweller or watchmaker for a quick and inexpensive adjustment.
Q. Is there a risk the clasp opens accidentally during wear?
A correctly functioning butterfly clasp requires simultaneous bilateral button pressure to open, it cannot open accidentally with normal wrist movement. If the clasp opens with minimal pressure or one-handed, the locking springs are worn and the clasp should be serviced.
Related Articles
→ What Is a Butterfly Clasp? How It Works and When to Use One
→ How to Install a Tang Buckle on a Watch Strap
→ Every Part of a Watch Strap Explained