I hadn't thought about this in years, but it was forced into my consciousness recently.
I have a thing about flappy straps on back packs. Those of you who have lugged the green variety around should understand my lunatic obsession. When I get a new back pack, the first thing I do is set the straps to the correct length, then either cut off the excess strap or roll it up and bind it with insulation tape (black only). Or I cut a fair bit of strap off, leave a bit in case I need to loosen it later and then bind up the excess straps with tape.
There can be no flappy straps. All loose straps must be neatly tidied away.
I hadn't even realised I was doing this until Junior borrowed a back pack recently. When it was returned, all the straps were flapping loose - he'd pulled off the tape to adjust the straps, but then hadn't tidied them up again before returning it. (Actually, I found it on the floor in his bedroom under a pile of rubbish, socks and noodle packets when I had to go looking for it).
I was about to launch into a loud rant when I caught myself and stopped. How on earth was I going to explain the whys and wherefores of this non-flappy strap requirement? It was better to just shut up, find the insulation tape and tidy them up again.