I spent half an hour with a clerk at our local hardware (the kind with rows after rows of pull-out boxes) trying to find one stupid screw that would fit my back brace. The one that worked had metric threads but the length was measured in inches. I bought four just to have backups.

Of course they were nothing they had in regular stock, so they just ripped open another box of the same model and got the needed parts off the shrink wrapped cardboard parts thingy.
I guess the next guy is also screwed.

Kudos to Lowe's, anyway.

Just recently had the light switch on a ceiling fan go out. I had bought the fan about six months ago, so no receipt, but fortunately they were still stocking the fan and the guy just ripped open a box and gave me the part. Probably could've tore the fixture apart, but finding a similar switch would've been iffy. Made life a lot easier just replacing the fixture.

There are at least 6 different American standards, at least 2 different British standards, and dog knows how many metric standards.

It took me weeks to figure out my Italian made espresso machine, sold in the US, used British pipe thread standards.

You hand them a thing-a-mahoogie and tell them you need the bungery-bor that fits on the other end and they always have it in the back.