A railing or rail was a long bar that protected against falls from high heights. It could also be used to hold onto when climbing stairs.
In 2152, Trip Tucker sarcastically offered to polish all the handles and rails in Enterprise NX-01's Engineering while the ship unexpectedly changed course for the Pernaia system. After Jonathan Archer gave him a look, he decided to purge the impulse reactors instead. (ENT: "The Seventh")
In 2369, Quark berated Rom for returning a patron's full currency pouch, giving him the punishment of polishing every rail in Quark's. Soon after, spying a lazy Nog, Rom passed on the punishment to him. (DS9: "The Nagus")