ARC Muzzle Grommet (Patreon)

A detail of those big silver buttons at strategic points around the muzzle.

The key will of course be attached to a robot arm.  The key is inserted into the slot then turned 90° to lock in.  Stops inside (not shown) prevent the key from being turned more than a quarter turn.

Once locked, the robot arm has full control over the movement of that particular point.

One anchor alone is not really strong enough to hold on to a head with a strong neck, so there are several on the muzzle that are meant to be engaged simultaneously.

These are mainly used at the feeding stations to prevent inmate's head from moving while the feeding nozzle is inserted.