Bound and Gagged
Japanese gags are some of the cruelist devices I've ever seen. The gag does not only restrict the mouth, it is a secure attachment point. A rope wrapped around the head and across the mouth will not slip, and this is used to pull the head back.

Another severe gag I've seen uses chopsticks to secure the tongue. One chopstick is above the tongue, the other chopstick is underneath. Fine twine secures the device and the tongue is pulled out of the mouth and immobilized.

Gags increase the captive's helplessness and humiliation. A gagged captive can't even beg for mercy. It is a cruel bondage Master who uses a gag.

C. Guilt's Bound and Gagged Series consists of beautiful naked Japanese and Asian women photographed in difficult positions.