Build an Under-Window Bookcase

Now that the basic bookshelf case is completed, we'll attach the plywood back. Using your Table Saw or Circular Saw, cut the 1/4" plywood to 47-1/4" x 24".

With the assembled case still face down on the table, check the unit for square. Using your tape measure, determine the distance across the back of the unit from the top-left corner to the bottom-right corner (this measurement should be somewhere in the neighborhood of 55-5/8"). Make a note of the exact distance, and then measure the distance between the opposite two corners. The two measurements should match. If they don't, the unit is out of square and needs to be adjusted. Simply move the case by pushing against the side of the case on one of the two longer corners, and then measure again. Repeat until the unit is square.

Now that the case is square, place the plywood back into the four rabbets. It should fit snugly and recess flush with the back of the case. Re-check the case for square, and then attach the plywood back with finish nails (no glue).

Stand the unit up and place it on the floor.

Now, you're going to attach the top (that you cut as the last item in Step 2) to the cabinet. This piece of 3/4" plywood should sit evenly with all four faces of the cabinet. Pre-drill and attach the top with screws from the underside, from inside the case into the top. Do not drill and screw from the top down, as the screw holes will be visible in the finished product.