A loose fitting nail placed into these holes will hold the door in place. Attach a small screw to the front of the door to use as a doorknob. The house may also be built with a fixed, instead of hinging, door, but this will make it more difficult to clean out should birds nest in it before it is inhabitated by bats. Apply a coat of polyurethane to the outside of the house only. Place at least ten feet high on a building or tree.
Southern exposure is best.