Percussive maintenance was a form of repair involving less-than-delicate handling of the repaired device or system. Despite the logically counterproductive methods though, it was often surprisingly effective.
The Tellarite Jankom Pog was an expert in percussive maintenance. He employed it extensively while repairing the newly-rediscovered USS Protostar, and managed to make the disrepaired starship flyable in less than a day. (PRO: "Lost and Found")
Due to his ambitions to join Starfleet, Jankom later attempted to adopt a more polite personality and as such, he began doing things by the book and discarded performing percussive maintenance. (PRO: "Into the Breach, Part I", "Into the Breach, Part II", "Who Saves the Saviors") However, in a moment of frustration, Jankom slipped back into his old habits and hit the console of the Infinity, causing the ship to power up, much to his delight. (PRO: "Temporal Mechanics 101") Jankom subsequently discarded his more polite personality for good. (PRO: "Observer's Paradox")
When the crew's holo-duplicates switched personalities because of a glitch, Hologram Rok stated that she had some percussive maintenance to do in Cetacean Ops while Hologram Jankom told Rok he thought that she was going to do a wonderful job and expressed Rok's love for whales. (PRO: "Imposter Syndrome")
When Jankom used percussive maintenance to get the Runaway working, Captain Chakotay remarked that he liked it. (PRO: "Last Flight of the Protostar, Part I")
After Vice Admiral Kathryn Janeway used her combadge as a makeshift explosive to free the Protostar crew, Jankom admitted that he was impressed with her percussive maintenance. Janeway called it an old trick from her Starfleet Academy days. (PRO: "Touch of Grey")