This is my version of a "gate" - it's a wire closet shelf that hooks onto the ridge on the roof of the brooder, kept in place with a few bricks, and then further secured against the chain link fence. Nowadays I aim to have the opening be about the width of a brick at most.my "gates" are made of 9-gauge galvanized wire formed in U shape upside down with the opening in the chicken wire fence "weaved" around it, so the width of the gate is indefinitely adjustable