the weight of the coins on top hold the other coins in place... for a really basic display get 4 quarters put one quarter down on the table... now if you try to balance 2 other quarters side by side on top it wont' work they will keep falling but if you put another quarter on top of both it will hold them in place
.....Quarter
Quarter Quarter
.....Quarter
the forums wouldn't let me line up the words right so ignore all the periods...