How do you do mount a fender on a bike without a screw hole in the chain stay bridge? A P-clamp around the chain stay bridge solves the problem. This trick works on seat stay bridges too. But if you don't have a bridge at all things get more complicated.
It's surprisingly hard to explain, over the phone, how a fork crown daruma works. Perry made this great sketch that says it all. Note that all VO fenders now get Daruma bolts rather than front L-brackets.
here and here. Fender mounting instructions can be found here. And there is an article about choosing fenders here.
Finally, there are some clever riffs on daruma bolts and fender mounting at Patricks an open sketchbook blog.