Racks are designed to transfer dead and environmental loads from the collectors to the roof structure. Hardware secures the collectors to the rack, the rack is attached to the building surface(usually the roof and the structure then carries the loads to the ground. SWH mounting kits are usually available from the collector manufacturer to match the collectors' frame. Most mounting kits use clamps that are inserted into frame extrusions, and proprietary mounting hardware. This is in contrast to most PV racks, which can be used with most modules.