Abstract: A set of building components for children comprising a multiplicity of generally hollow blocks having at least one open face and at least one aperture through each of a plurality of closed faces thereof, and a plurality of nut and bolt fasteners adapted to extend through a pair of aligned apertures in butted block faces to enable fastening of said blocks together in a variety of combinations and configurations. The blocks all have substantially the same cross-sectional configuration and are formed to different lengths corresponding to integer multiples of the length of the shortest block. The apertures in the closed block faces are formed along center lines of the faces with at least some closed block faces on the long sides of the longer blocks having a plurality of apertures therein spaced from each other by integer multiples of one-half of the shortest block length.