The term DADO refers to a type of joinery used in woodworking. It is created by cutting a groove or channel across the grain of a piece of wood, and then inserting a matching piece of wood into the groove. The two pieces are then secured together with glue or nails. The crossword solutions for DADO are RAIL (4 letters) and DIE (3 letters). A RAIL is a long, thin piece of wood that is inserted into the groove, while a DIE is a tool used to cut the groove into the wood.