Measure the bookcase width to make sure it is wide enough to fit the bed frame.
Measure the height of the bookcase to determine where the headboard will begin. Mark the bookcase with a pencil.
Remove all bookshelves from the pencil mark down. Some shelves may be held in place with pegs, while others may need to be unscrewed.
Roll the bed frame over the bottom shelf base of the bookcase. Make a square where the bed leg will sit. The frame must sit level on the ground. Use a jigsaw to cut out the square, opening the bottom base enough for the bed to sit without losing stability. Sand the edges.