A small board with great potential… by TeaSer

Take a piece of board, as wide as the your partners behind + a little more.
Put a screw eye at either end, and drill a hole at the middle.

Squeeze a dildo ( or a buttplug ) into the middle-hole *ss*

Then you place a piece of rope in the hollow of your partners knee, upon which you tie your partners right wrist and your partners right ankle to the screw eye at the one end of the board, and your partners left wrist + ankle to the other. Then you sit your partner down, onto the dildo/buttplug, and tie the rope from your partners knees over your partners neck or maybe to the piercings in your partners nipples...

Unless your partner is a genuine Houdini, your partner will be trapped, or if your partner should succeed in getting the dildo/buttplug out it will be impossible to get it back in without help; which should be punished properly...