The retrofit support bracket is used to attach either: 100mm, 220mm or 300mm duct to an existing 5/8" UNC threaded rod; which cannot be removed. It is simply a straight bracket with a slot for fitting to existing 5/8" UNC threaded rod. A locking tab is included which enables fitting to threaded rods. The support bracket is secured to the 5/8" UNC threaded rod by 2 x 5/8" Hendry split nuts and 2 x 5/8" washers. The Hendry split nuts can be fitted onto an installed threaded rod. A duct mounting bracket can subsequently be attached to the support bracket. These are for 100mm, 220mm and 300mm duct (Part No's: TC1279-14, TC1279-13 and TC1279-297) and are available separately.