Out on a ride with friends of various ages, we were coming back through East Grinstead.
Coming the other way were a couple of youths, pushing their bikes and looking a bit forlorn. Glancing at the handlebars of on of the bikes showed they were Not Right, having slipped from the tender grasp of the stem. I asked if they were OK and they confirmed they were not and did we have a <mimes twiddling a tool>. I indeed did have a <mimes twiddling a tool> in the shape of misc allen keys.
It was a quill stem with a single bolt squeezing shut the pinchy bit. I tightened it up, hoping hard that I didn't shear it off, as I gave it three white knuckles of torque - the splines on the bars didn't look brilliant.
Then I also noticed the head set was loose, so I tightened it as best I could by hand and told them what to do to get it fixed properly when they got home. They were very grateful and ever so polite.
They fared a bit better than the young lad I encountered a couple of weeks ago on the Downs Link, peering at his wonky looking Boardman MTB. He'd almost correctly diagnosed a bolt was missing, such that the rear suspension wasn't attached to the frame on one side. He hadn't noticed, until I pointed it out, that the lug the bolt went through had sheared off. I couldn't fix that one but made sure he was safe (only a mile to walk and his keepers knew where he was)
Oh, and two miles into today's ride, one of our number had a crank part company from the BB spindle. The nut (rather than bolt) was AWOL. Arse. I carry misc nuts, screws, washers and bolts but not a spindle nut. That was nearly a show stopper. Another member of the team set off back to scout the ground for it, something I didn't hold much hope of success. She'd gone all of 10m when she spied it on the deck. Hurrah. Deployed the crank extractor and lots of torque and all was well.