For when a clamp is not possible I have been doing some remodeling which included replacing the kitchen cabinets. The sink base for a corner unit came in pieces. The 45 degree angles of the front face to sides needed to be attached and glue was the only real answer. The sides are essentially MDF with a veneer. This material does not hold fasteners well, nor was it possible to use screws through the front which would have marred the finished look. It was not possible to clamp this assembly in place without extrodinary efforts. A quick... more info