- Whichever means of shelf attachment is chosen, an important consideration is the shelves' spans. A long span with no support under it will tend to sag when loaded with books. One remedy for this is a vertical support piece placed midway along the self, supporting the shelf from underneath and resting on the shelf below. This pattern would have to repeat from the top shelf to the next shelf down, then the next, all the way to some solid means of support at the base. These vertical supports reduce overall shelf space but not by very much, and they serve as dividers which in themselves can be useful.
- The framework of a freestanding bookcase will tend to rack or twist. A good way to prevent this is to have a backing board of something like ¼-inch plywood firmly attached. This makes the framework rigid and will also keep books from sliding off the back of the shelves if there's space between the bookcase and a wall.
Joints for the boards forming the bookcase top and the very bottom shelf, where these horizontal boards meet the vertical side boards, can be rabbet joints. Rabbets are strong, permanent joints, and since there's no need for these boards to be adjustable, the rabbet is a good choice here. - Freestanding bookcases---especially tall ones placed on carpet and loaded with books---can be hazardous. As long as the center of gravity is keeping the case upright, there may not seem to be a problem. But if a small child or a pet were to climb on or paw at the shelf face, tilting it outward, disaster, injury or even death could result. If there are no small children or problem pets in the house, a freestanding bookcase can be merely shimmed under the bottom at the outer edge. This should persuade the case to lean slightly backward toward the wall. But if there are small children around, the bookcase should be attached at the back with angle brackets to studs in the wall. This attachment doesn't have to hold a lot of weight; it simply has to keep the case from tilting away from the wall and toppling.