These bricks interlock by means of studs and look similar to Lego bricks in that the studs are laid out in a 4 x 2 pattern on the standard size brick. Produced in wood, during the ?s later made in plastic but both have a distinctive vertical grooving on the outer faces which simulates smaller bricks. These are collector items. Call Tom Taylor at 516 848 or email me at Tom@mag4lists.com