This article is from the Bicycles FAQ, by Mike Iglesias with numerous contributions by others.
From: Chuck Tryon <email@example.com>
Actually, I have used plastic like this (or in my case, some
red plastic from a cheap note book cover -- it's heavier) to extend the
bottom (rear) end of the front fender. The Zephals are good, but they
don't stop the splash from where the tire hits the road from getting on my
feet. What I did was cut a small triangle about 3in (~7cm) wide by 6in
(~15cm) long, cut a hole in the top of it and the bottom end of the fender,
and use a pop-rivet (with washers to prevent tear out) to attach it. On a
road bike, it should be end up being within a few inches of the road. ATB's
will need more clearance, so this won't work well off road.
| | | | /| o |\ <----- rivet with washer on inside | \___/ | / \ <---- flap fits inside of the fender, and follows the | | curve, which gives it some stiffness. | | | | \_________/ | | | | <----- bottom of tire \_/