The "zero clearance" concept is simple: The blade cuts its own perfectly sized slot by being raised through a machinable "blank" insert. Leecraft inserts are 1/2-inch-thick, high-density phenolic laminate, with bonded-melamine surface. They offer superior rigidity, flatness, durability, and low friction. User-friendly features include top-accessible leveling screws, lateral adjustment screws for a vibration-free fit, rear anti-lift pin (except JT-1), and a precut-blade bottom pocket that provides clearance for fully retracted blades and bevel cuts. Instructions included. Use carbide-tipped blades only. Fits Craftsman (Sears). Size: 14 by 3-3/4 inches.