Air conditioner side panels are installed after the window air conditioner is in place by using the panels that pull out from the air conditioner or with a universal kit. The latter is usually used when the original side panels have aged beyond repair.
Once the air conditioner is in place and secured by the window frame and sash, the side panels, also called curtains, may be pulled out from the side of the unit. They are located near the front of the air conditioner, next to the lip that locks into the bottom of the window sash.
Each panel is pulled out to fit into the empty space on each side of the air conditioner. They look like small accordion doors and are held within a frame for stability. The panels are pulled out to cover the gap between the sides of the air conditioner and the window frame. The panels can be left as is or fastened to the window frame on the top and bottom for a more secure fit, using pre-drilled screw holes.
If the panels are worn, universal replacement kits are available that fit most window air conditioners. The old side panels slide off the unit, and the new ones fit right inside the same grooves on the top and bottom. The air conditioner should be removed from the window before the replacement.