Some libraries, especially those serving the general public, use book drops so that readers may return books when the library is closed. Using book drops is best avoided, but if the circumstances require it, a few caveats should be observed.

The drop should be a hinged slot in the wall or door of the building, to avoid the risk of damage that curbside book drops can suffer when struck by a motor vehicle or engulfed by a street flood. The books should drop no more than 20 centimeters, and they should land on a spring-loaded surface that allows the books to sink into a box container. The entire book drop structure should be in a metal container to prevent arsonists from setting the building on fire through the slot.