Cisco Ceiling Grid Adapter for suspended channel and beam rails. The AIR-AP-T-RAIL-R and the AIR-AP-T-RAIL-F will mount directly to suspended ceiling grids who use T-Rails (the most common kind). For those suspended ceilings that use channel or beam rails, the use of the AIR-CHNL-ADAPTER is needed to mount the AIR-AP-T-RAIL-R and AIR-AP-T-RAIL-F.