DIAGONAL TOY PIECES AND THEIR CONNECTION

A diagonal toy piece for a modular toy building set including an underlying support structure for supporting the diagonal toy piece and other toy pieces. The diagonal toy piece is a generally planar member having a top side and a bottom side, two outside edges having respective outer ends spaced from one another, and a diagonal edge joining the outer ends of the outside edges. For mounting the diagonal toy piece on the underlying support structure, the bottom side of the toy piece has an attachment fitting removably attachable to the support structure. The attachment fitting is preferably spaced from the diagonal edge of the toy piece. The diagonal toy piece can be joined with another, complementary diagonal toy piece via a connector on its diagonal edge which is releasably connectable to a cooperating connector on the complementary diagonal toy piece. The toy building set includes a plurality of generally planar toy pieces mountable on the support structure, including one or more of the diagonal toy pieces or composite toy pieces.