The Tongue & Groove Angle with a 1 3/8" x 1" size and a 1/4" shank is a woodworking router bit designed for creating tongue and groove joints. This bit features a 1/4-inch shank, making it compatible with most routers. The 1 3/8" x 1" dimensions refer to the profile of the bit, which is ideal for cutting precise tongue and groove joints in wood pieces, commonly used in cabinet making, flooring, and paneling. The angle ensures a secure, smooth-fitting joint, providing strong and professional-grade results.