The bite calls work similar to crow call guts. Just squeeze the two toneboards together with your teeth, and if you vary the pressure, it will vary the sound. The tighter the pressure, the higher the pitch. The bite call guts are really intended to imitate a cow elk, but you can also do some bunny in distress as well.
My brother called in a yote once with a Sceery bite call, but our horse in that pasture spotted the coyote about the same time as my brother did. The coyote was about 75 yards out, but the darn horse was chasing the coyote away!!! My brother kept calling, and the coyote kept wanting to get closer, but the darn horse was playing keep away.
It was kinda comical and should have been on the blooper reel if we were videoing. :D
Brian