Decide how large you want the wall unit bookcase to be. Use a measuring tape to measure the width and height of the area on the wall where you want the bed and bookcase to sit. Place the bed against the wall while taking your measurements to help you visualize the size of the bookcase.
Purchase a wall unit bookcase that is equal to the dimensions taken in Step 1.
Position the bookcase on the wall. Set the bed in front of the bookcase to determine exactly where you want the bookcase to sit. Make adjustments, as necessary.
Place a pencil against the wall where the top of the bookcase sits on the wall. Draw a line along the wall across the top of the bookcase. Remove the bookcase from the wall.
Locate two studs in the wall along the pencil line with a stud finder. Draw an X on the pencil line where the studs are located.
Place the bottom part of an L-bracket against each of the X marks; the angled part of the brackets should sit at the top of the pencil line. Place a pencil in the holes on the bottom of each of the L-brackets and make a mark on the wall to indicate where the holes will sit. Remove the brackets.
Drill through each of the pencil marks that indicate where the holes on the brackets are located, creating pilot holes for the screws.
Place the brackets back on the wall so that the holes in the brackets are positioned over the pilot holes. Drill 3-inch wood screws through the holes on the brackets and into the wall.
Position the bookcase against the wall; the top of the L-brackets should rest against the top of the bookcase.
Drill 1-inch wood screws through the holes in the top of the L-brackets and into the bookcase.
Position the bed against the wall unit bookcase.