Parts a little out of shape? These brackets are the best I've found. They're a little bulky and a little difficult to master, but once you do, they're golden. Within reason, they will cause all imperfect boards to become square. I made blocks to fit under the clamps to lift them off my workbench so I can install pipe clamps and parallel clamps on the underside to pull the boards together. The left and right sides of the clamps are parallel and flat so the parts will automatically lift - again within reasonable limits. I use wood washers on all four clamping surfaces to avoid damaging the work piece and I made a 5/8" wide 1/4" flat washer that fits into one of the clamping channels to secure the 1/4" tab on the to allow back wall six bookshelves i am building the angles between the cabinet and the shelves are perfectly even there are blue ones from another company they are good and good quality but they are used to hold parts in place that are already square They are great for imperfect boards.