We have a hanging balcony off of a second study bedroom with a sliding glass door and a small waist high window.  We were able to quickly assemble the cat enclosure. Then we removed one of the higher screens & positioned the open wooden pane snug over the small window.  Now the cat can access the enclosure through the small window.  Our indoor cat was so excited to be in the outdoor enclosure he stayed in it for over a day without coming back in the house.  He just loves his safe and protected “catio.”