The 1.5" diameter entrance hole is specifically designed for bluebirds, and the absence of a perch deters more aggressive cavity nesters. Ventilation gaps in the top corners of the house keep the interior temperature regulated, and a slot at the back of the base allows water to drain from the nest. The 0.8125" thick cedar construction aids in insulating the home, and the lapped roof adds drama. The front panel lifts upward, making cleaning and nest checks simple, and a metal latch keeps it closed. Use the included screws and predrilled mounting holes to attach this home to a post or pole.