Quiet a Rattling Bolt
The issue: The noise from your bike is driving you crazy. You find that one of the stem bolts has rattled out, and you don’t have a spare.
The solution: Steal a bolt from the waterbottle cage using your multi-tool. Remove the old headset bolt and replace it with the one from your waterbottle cage.
Keep in mind that not all bolts are created equal, and engineers specify thread size depending on anticipated stress. There are a few common bolt sizes on bikes, and waterbottle cage bolts will work in a few handy locations, the headset being just one of them.
But remember, waterbottle bolts might not be the right length, they might be made out of aluminum, and aluminum bolts shouldn’t be used for anything critical. Don’t be lazy—get a proper replacement for the bolt when you finish your ride.