3/8 is such a cursed measurement lol. Like this 3/8 wrench fits a #10 hex head screw. No it doesn't fit 3/8 hardware. You want 9/16 for that. Oh 9/16 hardware? You can use either 7/8 or 13/16. Or just grab a metric wrench that's close enough like a 7/16 is the same thing as an 11mm or 3/4 is the same as 19mm. Not gonna lie at certain point it's just memorizing shit and pattern recognition