Escape mechanism for sliding block puzzles

In a sliding block puzzle comprising a game which includes a plurality of frame members and a plurality of blocks slidable within the frame, the blocks mating with each other and the frame by means of tongues and grooves disposed in complementary relationship on adjoining ones of said blocks and by grooves in the inwardly facing walls of selected ones of said frame members and by tongues on the inwardly facing walls of the remaining ones of said frame members, said tongues and grooves cooperating to retain the blocks within the frame, wherein the improvement comprises the modification of the tongue along a section of one of said remaining frame members and the modification of the groove of one of the blocks, the modifications being such that when said one block is positioned adjacent said frame member section the block can be removed from the frame.