Window Experts Single or Double Casement Doors are suitable for opening-in and opening-out mode, can be used as main entrance door or as ancillary door leading onto corridors, Patios or balconies. Casement doors are available in 62 mm or 112 mm profile depth and can be manufactured as stand-alone items or part of a screen incorporating fan lights and/or side lights. Double doors also known as French doors can be used as an alternative to sliding Patio doors, especially, when a clear wide opening is being desired.