Imagine two coins is on your spectators palm and they sign it,after that you ask them to close their fist and you wave your hand over,and when they open their hand and try to separate it,the two coins are now melted into each other and fused forever,Welcome to SOLID.

IDEA // You approach to a table with two young couples,you then show the coin and say that let see the future if they are really for each other the coin will stick.you ask them to signed both of the coins and ask them to put the other ones hand on the top,after that when they open there hand two coin is now fused and they can't separate it. so they are destined to be with each other forever.

Immediately hand the coin for examination
Easy to do
Easy to find gimmick