Purchase this drop door kit if you plan to place your Royal Victorian greenhouse on top of a perimeter wall. - usually 20" - 36" high (24" might be best). Because perimeter wall heights can vary from 20" - 36" high, this kit does not include the extra polycarbonate or glass panels needed above the door. Ask us about extra polycarbonate or glass. NOTE: We strongly recommend upgrading to Hinged Doors (sold separately) when the greenhouse stands on a perimeter wall. Perimeter walls can prevent doors from sliding if not aligned flush.