Type 11 T-rail suspension is a method of suspending D-shaped ducts, making it ideal for low ceilings. The T-rail, so named because it looks like a T in the cross section, is made of anodized aluminum, making it an excellent choice for corrosive environments. Two T-rails are fixed to a hard ceiling and the duct is then suspended from the rails. The duct will have a bulb edge at the 3 and 9 o’clock positions. The height of the bulb edge above the duct can be manufactured to specification.