A hollow block (e.g. a rectangular prism) preferably has six (6) perpendicular faces. Each face preferably has a wall with a particular thickness. An opening is provided in at least a particular one of the faces, and preferably in all six (6) faces. A hollow beam (e.g. a rectangular prism) preferably has six (6) perpendicular faces. Each face is preferably defined by a wall with a particular thickness. An opening is provided in at least a particular one of the faces, and preferably in the four (4) faces defining a closed loop, in the beam. Substantially parallel snaps extend from the other two (2) beam walls and have at their outer ends portions shaped to facilitate insertion of such snaps into the opening in the particular face of the block, retention of the snaps by the inner surface of the face defining the opening and removal of the snaps from the opening. Such portions are shaped for the beams to be pulled, peeled or bent from the block. When the block has an opening in each of its six (6) faces, snaps from six (6) different beams can extend into the six (6) different openings in six (6) different directions in the block without any interference in the block from the snaps in the six (6) beams. In this way, complex structures can be formed from the blocks and the beams. Other structures such as vehicle ramps, building roofs, awnings and corbels can be disposed in a cooperative relationship with a structure formed from the blocks and the beams.