They can enter various ways. One is if the flashing around your chimney is loose, they squeeze in and roost on the rafters. Another is the end gables venting system. When installing the rake boards a space is left and they can work inside through cracks. I have had them in my office in the basement. They came in around the chinimey and fell down to the basement. It feels weired when you are working at a drawing board and one whizzes by your neck. I usually shut off the lights and open the door. I go outside and watch for them to find their way out. If that doesn't work a tennis raquet is the weapon of choice. They have trouble avoiding it as their echo penetrates and they fly right into it. Nasty looking critters!
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