Dell has created several variations of server rack mount rail kits for their various PowerEdge and PowerVault servers and storage arrays.
Versa Rail - This is used for installing Dell rack mount systems into server cabinets that are not made by Dell. These cabinets normally use threaded mounting holes.
Rapid Rails - This is used for mounting Dell rack mount systems into server cabinets that are made by Dell. These use square holes and utilize Dells tool-less installation.
Dell has now created two more options for their rail kits. The Static and Sliding ReadyRails. Static rails are designed to only extend far enough to install or remove the system from the cabinet but not enough to access any top panels for service. The ReadyRails completely extend allowing full service access to the top of the Dell system without having to remove it from the cabinet.