Buttplug.

The idea with this buttplug, is that the buttplug will insert smoothly, but upon turning the key, it will be stuck !
The drawing is in four parts:
1/A buttplug, & a key.
2/Here I've cut away a bit of the key, and fitted it to the end of a steel T.
   At the same time I show the locking mechanism inside the buttplug.
3/Here you see the key, as it is inserted into the lock, vith the t-bar just outside the buttplug.
4/Finally the key has been turned, pushing the bottom-plates out, widening the buttplug at the base by means of the purple 'arm'.
   (Now the cruel sadist removes the key, and the buttplug is stuck in place untill unlocked...
NB: For security resons, give the wearer the other key, in a sealed envelope - it's no fun to have a locksmith fubling around up his/her ass, if he/she is e.g. hospitalized..! )