Have a spectator step forward and tie the belt around their waist, so the snap part of the shorts and the matching snaps are towards the inside of his body. Attach a rope to each ring.
 
You stand to one side and have another assistant stand on the opposite side. Each of you holds a rope, stretched out full, and away from the victim. Instruct the person with the other rope that, on the count of ‘1---2---3’ they are to pull up and away on their rope. When this is done by the other person and you, the shorts will come up out of the belt to the front of the victim.
 
When this move is done quickly the shorts will be in front of the victim between the ropes, so fast they can not see where they come from.
 
A BIG laugh!!
 
Condition Notes:  Looks to have never been used, though it may show slight signs of age or storage wear.