A Navy acronym
. The maintenance or repair technique
for restoring to service materiel thought to be scrapable. Frequently used in cases where the repairer has no idea how/why a fix worked, only that it did.
Pure Fucking Magic.
CPO: "Tell me, Seaman Beaumont, how did you get that busted framajamit valve to work again?"
SB: "Well, Chief, I took my BFH and gave it a bit of percussive maintenance. That loosened it up a bit, and the rest was PFM."