Abstract: A construction kit comprises male and female elements, preferably of molded plastic material, for assembly into various model structures. The male elements have cubic bodies with studs protruding from two or more faces and the female elements are elongated U-section pieces having corresponding square end walls with keyhole-shaped openings for receiving and gripping shanks of the studs whose heads are guided and held between the lateral walls of the female elements. The male elements can be formed of interengaging pieces, and may possibly be pivotally joined. The kit may include various accessories such as panels, struts, pulleys, wheels with removable toothed rings or tines, a motor and so forth to complete the desired structure.