In The Force Awakens, Rey is shown salvaging components from cylindrical structures in a crashed Star Destroyer's hangar. Is there any information (cue the TFA Visual Dictionary, Incredible Cross-Sections, etc.) on the function of those components and what they're called?
UPDATE: According to the Force Awakens: Visual Dictionary they were "Capacitor Bearings". Quite why a capacitor needs a bearing isn't explained.
The script describes them as "various mechanisms"
A metal sheet is pulled open to reveal the wrapped up faceof A SCAVENGER, perhaps alien, in GOGGLES, FACE MASK and GLOVES. Backpack with a STAFF strapped to it. Uses TOOLS to remove various MECHANISMS from inside the wall. We are in an upside-down, canted CORRIDOR. The Scavenger finds a valuable piece, drops it in a SATCHEL.
The Junior novelisation is similarly enlightening, referring to them as "various components"
She hung on to the wall of a demolished destroyer and used her tools to wiggle free various components that rust hadn’t devoured. The ship was a treasure trove of metal sheeting and military-grade tech that, if given a proper cleaning, could fetch Rey a meal or two at Niima Outpost.
The Official Novelisation is just about as forthcoming, noting that they're "small devices"
Wielding an assortment of tools, the scavenger was excising an assortment of small devices from one metal wall. One after another, bits of booty found their way into the satchel that hung below the slender figure.
When the satchel was full, the scavenger secured it shut and commenced a perilous descent, avoiding sharp projections and threatening gaps in the wall. Arriving at the bottom of the metallic canyon, the figure hefted a piece of larger salvage recovered earlier and then, laboring under the double load, headed toward a distant slit of sunlight.