The galvanized steel hooks are always assembled on the ductings at delivery; ready to hang up. The hooks are to be hooked on a longitudinal steel wire, fastened by rock bolts in the tunnel ceilings. The suspension is constructed in such way, that if there would be an extraordinary force on the ducting, the steel hooks will break and leave the reinforcements without damage. Steel hooks are available as spare parts and can easily be reassembled on the ducting.