The jaw is the lower half of a puppet’s mouth — the plate the performer’s thumb drops to open the mouth, and the moving part in every lip sync.

The thumb drops; the head does not lift

This is the single most important rule in puppet performance and the jaw is where it lives. The fingers and palate stay level in space, and the thumb comes down and returns. Get this and everything you shoot improves immediately.

Sizing

Trace the performer’s thumb separated from the flat of the hand and build to that. A jaw that is too large flaps loose and cannot be controlled precisely; one that is too small cramps the thumb within minutes.

Weight matters here more than anywhere

The thumb is doing all the work, on its own, for every syllable of a performance. A heavy jaw is exhausting in a way a heavy skull is not, because the skull is carried by the whole arm.

The chin

The visible chin and lower lip build onto the jaw plate, and their shape does much of the character work. A prominent chin reads as strong or stubborn, a receding one as timid. Keep the foam here thin at the corners or the mouth will not close cleanly.

The hinge

joining jaw to palate should be a flexible strip — fabric tape, fleece or thin leather — not a crease in the board. A creased plate cracks along the fold within a few dozen opens.

The hack: build the jaw, hinge it, and work it a hundred times before you skin anything. Every mechanical problem shows up in the first hundred opens, and all of them are fixable while the plates are still bare.