Really run-of-the-mill set of mouthplates for puppets. I use gaffer's tape to put them together at the straight edge end. Work really well with flexible material.

I print these plates and tape together if I want a fixed jaw. Alternately, I might have a more movable "floating jaw" and use no tape to hinge them together. I then cover them in felt or whatever material a puppet's mouth will be made from, hot gluing the material to cover both sides. I add finger-holds onto the back and a tongue, teeth or other details to the front side. From there, the mouthplate is glued securely into the foam head of the puppet.