Measure the wall’s dimensions where you wish to turn into a wall bookcase. For example, your wall may measure 10-feet wide by 8-feet high. Measure the dimensions of your old bookcases from outer edge to outer edge. For example, you may have one that is 6-feet long and 4-feet high, two that are 3-feet long and 4-feet high, and one that is 4-feet long and 8-feet high. These fit perfectly on the wall. The bookcases should all be the same depth.
Finish the bookcases so that they look the same. You may wish to paint them all the same color white as the walls in the room. Before painting old bookcases, remove old paint or finish with a liquid stripper. Cover the ground with a drop cloth or old newspapers in a well-ventilated area. Paint on the liquid stripper with a large paintbrush using long strokes. Follow the wood’s grain of the wood. Allow it to sit according to manufacturer's instructions. Scrape off the stripper and old finish with a plastic or metal paint scraper. Discard the scrapings.
Sand the bookcases lightly with fine-grade sandpaper. Apply primer to the bookcases with a large paintbrush following the wood’s grain and let it dry for at least four hours. Apply one or two coats of paint to the bookcases with a large brush following the wood’s grain. Allow to dry thoroughly.
Studs are vertical, wooden boards under the wall. Turn on your stud finder. Start at the wall’s left side. Place the stud finder on the wall and mark with a pencil where the first stud is located. Measure from that spot every 16 inches across the wall and mark with a pencil every 16 inches.
Arrange lower level of bookcases against the wall. In the example above, arrange the 6-foot long and 3-foot high bookcase next to the 4-foot long and 8-foot high bookcase. Match the pencil markings on the walls with points just above each shelf in the bookcases. Using a power drill, drill two screws through the bookcase into the stud above each shelf in the bookcase. This permanently secures the bookcase to the wall.
Arrange the remaining bookcases on top of the 6-foot long bookcase. Screw into the wall where the studs are as in the step above.
Use bookcase paint to touch up over the screws. Allow to dry, and place your books in your new, wall bookcase.