I built a box about 10" x 10" x 6" and placed it 15 ft off the ground. It does not have a round hole in it, but the top 3" of the front is open. I placed it on a larger oak tree thats clean of limbs up to the 15' mark. The box stays in the shade of the canopy all day with some filter light and faces the east. I swear within a week a little screech owl was in it. They've been here for years now... Stephenville Tx.
mike