Jaw clamp

What is a jaw clamp?

Jaw clamp (also called a jaw spreader or mouth spreader) is, in BDSM, a device that forces the mouth open, with a ring or with a screw mechanism. Unlike an ordinary gag, access is the goal, not silence. In Dutch, the same word, kaakklem, means exactly the opposite in medicine: a jaw that won’t open.

Why the Dutch word means two opposite things

Because the scene word is younger than the medical one.

In medicine, kaakklem has stood for trismus for over a century in Dutch. Oral surgeons J.A. Baart, R.B. Greebe, and H.C.J. Kerstens of the Vrije Universiteit write in the Nederlands Tijdschrift voor Geneeskunde that trismus is not a condition in its own right but a sign whose cause you have to track down, and they call it in the same breath “this kaakklem”. The word trismus comes from the Greek trismos, grinding.

In the playroom it’s flipped. There the object is named for what it does to the jaw, not for what the jaw can’t do. So anyone who meets the Dutch word in a medical context is reading about someone who can’t get their mouth open, not about a tool.

Why people use a jaw clamp

A jaw clamp doesn’t silence anyone. Medical spreaders of the Whitehead or Jennings type stop coherent speech, but sound still comes out just as much.

What to watch for with a jaw clamp

The clock, because the jaw joint has no safeword.

A jaw clamp does on purpose what a yawn does by accident: opening the mouth wider than its own resting position. Kunihiro Yoshida counts in Medicina all published cases of a jaw joint that stayed out of its socket for more than a month, and yawning is the most common cause at 14.4 percent, ahead of surgical procedures (8.3 percent) and neurological disorders (6.6 percent). His explanation is exactly what a spreader forces: a mouth opening that goes just a little past normal.

In practice that means three things. Set the ring or the screw to the opening that comes on its own, not the opening you can force with a push. Keep it short and take it out before the jaw starts to tremble. And set a signal that needs no voice, because a voice is exactly what falls away here; what that looks like is on check-in.

Where this fits on this site

Gags are part of the bondage work on my yes-list, and the spreader is the variant where access is the goal. What happens on an evening like that and how we go through beforehand what is and isn’t on the table is on the BDSM date.

Sources

• Trismus als symptoom. J.A. Baart, R.B. Greebe & H.C.J. Kerstens, oral surgeons at the Academisch Ziekenhuis der Vrije Universiteit, Nederlands Tijdschrift voor Geneeskunde 131, 147–151, 1987. Provides the medical meaning: because trismus is not a condition in its own right but an expression of an anatomical, physiological, or pathological fact, it’s necessary to track down the cause of “this kaakklem”, and the origin of trismus from the Greek trismos, grinding.
• Long-Standing Temporomandibular Joint Dislocation: A Comprehensive Review and Proposal of a Treatment Algorithm. Kunihiro Yoshida, Medicina 61(9), 1505, 2025. Provides the distribution of causes for jaw joints that stayed dislocated for a long time: “The most prevalent etiologies were yawning (14.4%, n = 33), surgical procedures (8.3%, n = 19), and neurological disorders (6.6%, n = 15)”, plus the explanation that such dislocations can arise with a mouth opening that falls just outside the normal range.

Related terms

• Gag. The umbrella of which the jaw clamp is the mouth-holding-open kind.
• Ballgag. The same strap, but with a ball that fills the mouth instead.
• Bitgag. The in-between form, with a bar behind the teeth and the jaw half open.
• Deep throat. What the access a jaw clamp gives is usually meant for.
• Stop signal. The sign you need the moment speech falls away.
• Mouth spreader. The synonym, with the two builds and the surgeon who drew the design in 1876.