It's just like a big belt really that wraps round your waist with the buckle and padded bit at the front. Passenger holds on to the imitation 'love handles' that hang just to the front sides of your waist which means that when you brake their weight is distributed lower and not onto your back and therefore onto your arms (which makes it difficult to control steering). My youngest had a bit of trouble reaching the handles, so I just flipped the belt round so that the handles were further back and she was well happy! ;D
Only trouble I have now is going for a ride on my own... nearly always hear a shout of "Can I come!?" from one or both of them! :-\