Abstract: A unit block toy adapted to compensate for slight size variations can have a pair of opposed side walls adapted to be disposed over at least a portion of the unit block, and a gasket disposed on an inside surface of at least one of the pair of opposed side walls, the gasket being adapted to compensate for slight size variations. The gasket can have a concave side and a convex side, the concave side positioned adjacent the inside surface of the adjacent sidewall such that a space is formed between the gasket and the inside surface to permit adjustment for size variations via displacement of the membrane towards the inside surface. A slot can be provided in the inside surface of the side walls in which to dispose the gasket.