The wings on most aircraft are removable, and are held on by bolts of appropriate size. Smaller aircraft may have left and right wings built as a single assembly, while larger aircraft will have separate left and right wings. The C-130 Hercules follows the latter pattern, and each wing is held on by a set of 14 bolts, the individual bolts being about six inches in diameter, about four feet long, and made of incredibly tough steel. They get replaced every 10,000 or 20,000 hours of flight, lest one fail and cause the wing on that side to flutter and eventually to depart the aircraft. My friend Mike was a maintenance shop chief, responsible for maintenance on a number of C-130 aircraft. It was close to time to replace the wing bolts on one, and he did what he'd done so many times before: send in a requisition for 28 each Federal Stock Number something-or-other, so that they'd be ready and waiting when the aircraft needed them. But something happened that had never happened before: he got a call from Base Transportation, asking where he wanted his boxcar to be parked. "Boxcar?", he responded. "Yeah. The boxcar full of crates of C-130 wing bolts. Where do you want us to put it?" Someone had changed the unit of measure for C-130 wing bolts from "each" to "set of 28", since all of them were always replaced at the same time. It made sense to do it. Somewhere in the mass of paperwork that had come over Mike's desk in the past few months, there doubtless was a memo notifying him of the change, too. He never found it, but he certainly remembered from then on.