Abstract: A system, used in the construction of furniture, is provided for joining at least two and at most four boards disposed at right-angles to each other, those end faces of the boards that face the zone where the joint is made being provided with interengaging toothed formations. The end faces of the boards to be joined are provided with raised portions, the cross-sections of the mutually contacting raised portions on four boards together forming a square. The raised portions comprise projections and recesses of a shape complementary to that of the projections and which extend into the raised portions and below and transverse to the projections.