Information on how to tighten a fixie chain by walking the wheel back.
Turn a freewheel or sprocket hub into a fixed gear. It's called a suicide hub because the gear is threaded on, with another lock nut following it. This can come off if it's not reinforced extremely well. The biggest danger is for brakeless fixies relying on the fixed gear to stop.
This guide uses loctite, and a comment says you can weld it too.
I have no experience on it, just learned of it yesterday. Proceed with caution.
A fixie, or fixed wheel bike, has a single cog fixed to the wheel, so it will spin forward or backwards with the cranks, but can't spin freely. You can put back pressure on the pedals to slow down, or lock your legs to skid to a stop.
Riding a fixie can feel more connected with the bike, since you're always in motion with it. You will find yourself speeding up your approach to hills and generally riding more efficiently.