tied genitals
I designed a device to lock a guy into a girl. It looks like a cuff for a handcuff but with 6 holes in either side of the closed cuff. Six, three each side, labia clamps attached to chains pull through the holes. When the clamps are pulled up to the cuff they are squeezed tighter. The cuff closes tight so it is also slightly painful. A lever on the keyhole turns when the cuff is locked preventing the chains attached to the cuff from being pulled out of the holes.
Had one made, works real nice. Now all I need is a girl who is willing to be locked in it with me.