(covers information from several alternate timelines)
A hand hold
Hand holds were part of a starship's interior that personnel could grasp to brace or stabilize themselves.
Multiple hand holds, shaped like metallic bars, were on the sides of corridors aboard J-class and Y-class freighters and NX-class starships. (ENT: "Broken Bow", "Fortunate Son", "Acquisition", "Horizon", et al.)
The Earth Starfleet vessel Enterprise NX-01 featured hand holds in all areas of the ship including the bridge, the situation room, the command center, sickbay, corridors, and the launch bay. (ENT: "Terra Nova", "Civilization", "The Catwalk", "Regeneration", "Impulse")
In 2233, the bridge of the USS Kelvin also featured various hand holds. (Star Trek)
The term "hand hold" comes from the final draft script of "Acquisition". In the final draft script of "Horizon", the term was formatted "handhold". Also, the final draft script of ENT: "The Breach" referred to areas of a cliff which could be used to cling to, while rock climbing, as "handholds".