Dado Bricks are interlocking cardboard bricks, measuring 12 inches long x 6 inches deep x 3 inches high. Kids can use these stacking bricks to create kid-scale structures...walls, castles, forts, secret hide-outs, or even attractive room decor. Unlike other simple cardboard blocks on the market, the Dado Cardboard Bricks contain a protruding pair of square nubs along with a matching set of recessed square indentations. The result is a cardboard brick that when stacked, will not easily tumble and can retain a rigid structure. "The ONLY interlocking cardboard block on the market," Erik Quam, Director of Product Development at Fat Brain Toy, told TDmonthly.