Step 3: Cabinets
Once you have the frames in the room, you can set the cabinets on the base. We set them flush with the front of the frames. Then we used a few drywall screws from the sides to connect the cabinets to the frames. Be careful on the placement so the screws don't go into the cabinets. Once the cabinets are in, the cabinet top shelf can be added, and screwed in.
Placing all the frames against the wall, and use shims to get the cabinet top shelves to line up and look straight. Once you have them lined up, use a few 1 1/4" drywall screws to connect the frames together on the sides so they don't shift. Pre-drill and counter-sink these holes too. We found white plugs to put in the counter-sunk holes. Wood putty and paint would probably work too - might not match the melamine finish exactly, but you really wouldn't notice once the shelves are in and filled with books.