Tongue and groove or T&G is a method of fitting similar objects together, edge to edge, used mainly with wood: flooring, parquetry, panelling, and similar constructions. Tongue and groove joints allow two flat pieces to be joined strongly together to make a single flat surface. Before plywood became common, tongue and groove boards were also used for sheathing buildings and to construct concrete formwork.

A strong joint, the tongue and groove joint is widely used for re-entrant angles. The effect of wood shrinkage is concealed when the joint is beaded or otherwise moulded.

Each piece has a slot (the groove) cut all along one edge, and a thin, deep ridge (the tongue) on the opposite edge. The tongue projects a little less than the groove is deep. Two or more pieces thus fit together closely. The joint is not normally glued, as shrinkage would then pull the tongue off.

The Carbide Tipped Tongue & Groove sets shown, are pre fitted from the factory to produce perfectly matched components.