Abstract: A construction toy set whose main component is a cubical open-top box, the bottom and side walls of which are divided into quadrants, each having a keyhole therein and a coupling collar encircling the keyhole and projecting from the quadrant. Also included in the set are cylindrical spacers that fit over the collars and extend therefrom, wheels having cylindrical hubs that can slip over the spacers which then function as axles, and hub caps that rest against the outer end of the spacers or the wheel hubs, each cap having a center keyhole matching the quadrant keyhole. The components can be assembled and interconnected to create different structures by means of connector bolts each having a key at one end capable of passing through the keyholes.