Hinged roofs allow you to easily open and close the house for observation. Boxes that open from the top are best. Boxes that open on the sides are also convenient but there is the possibility that the babies will jump out. If this happens just pick them up and place them back inside. The adult bird will not reject the baby if a human has handled it, this is a myth.
Most birds have a terrible since of smell.
Never put a hinge on the bottom of the box as this would cause the nest to fall out when you opened it. You should peek inside once a week and evict any House Sparrows, Starlings, squirrels, rodents, snakes and wasps. Rubbing a bar of soap on the interior roof will prevent wasps from building a nest. Watch the nest box for awhile. If you don't see or hear any birds, go over and tap on the box.