Solid wall wire retainers are inserted in the duct and snap into place. The retainer can be used on any smooth, straight run of duct and can work with vertical and overhead applications. Solid wall wire retainers are manufactured from black PVC. Slotted wall wire retainers snap in from the outside of the duct, allowing for fast and easy installation and removal. Slotted wall wire retainers are manufactured from black nylon 6/6.