Roll Forming Machine for steel Unistrut C Metal Slotted Strut Channel 21x21mm & 41x41mm for the suspension and fastening materials of planner, contractor or duct fitter. From channel sections/struts via various duct hangers through to pipe clamps and beam clamps you will find everything you need for the quick and easy suspension or attachment of ventilation ducts. A great advantage when using struts for suspension of ductwork is the fact that no additional screws or rivets affect the air duct.