I've seen some inventive repairs in my life, both in my bicycle work and theatre work, but yesterday a fella came in off the trail with an improvisation that really surprised all of us. Alas, I was unable to get a photo, but I'll try to describe in words what he did.
Apparently, somewhere along his ride, or perhaps over the course of several rides, 4 of his 5 chain ring bolts (chain rings are the big sprockets attached to the cranks that you turn with the pedals) had worked loose and fallen off the bike. When the rider realized this, he figured he needed a temporary fix to get him to the nearest shop, so he turned to something near at hand... grass stems! Seriously... he used a number of strong, fibrous grass stems to TIE the chainrings in place! The amazing thing is, it worked. I'm not sure how far he rode that way, but any distance is pretty remarkable.
So, next time you have a mechanical problem on your bike... maybe you don't have to reach for your cell phone first!