We were looking to replace a very similar air conditioner. After assembly and installation, I realized the side panels were on the wrong sides (they are not marked left or right, and the installation drawing is vague). The little square projecting feet at the bottom of each accordion side (where you screw the last two screws into the sill, unless like with our replacement windows, they are 2" up in the air) should face into the room.  So far it works fine.