Rails are a stage element in Specter of Torment, they are only found at Stranded Ship and Tower of Fate. Rails act similarly to the Conveyor Belts, defining the direction that Specter Knight will take, however they also include aesthetic changes (such as surfing animations) and the attempts to walk won' t change the direction followrd, just the speed.
Specter Knight can also equip the Rail Mail which lets him grind on any surface like on a Rail.
The player can perform stunts on rails by pressing "Up" or "Down" (depending on game device), these are just aesthetic changes to the jump and don' t influence the movement, however they are required in Darkslide the feat. Pressing the same directional button as the orientation of the Rail will increase the grinding speed.