Tongue and groove (T&G) joints allow two flat pieces to be joined strongly together to make a single flat surface. A strong joint, the tongue and groove (T&G) joint is widely used for re-entrant angles. 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 depth of the groove. Two or more pieces thus fit together closely. The effect of wood shrinkage is concealed when the joint is beaded or otherwise moulded. The joint is not normally glued, as shrinkage would then pull the tongue off.