This is a simple book holder that rests on the handlebars of my stationary bike so I can read while I'm riding.
Step 1: Materials
3 - .5" * 2.5" * 24" Poplar boards
1 foam sheet, available at Michaels, Hobby Lobby, etc.
2" hole saw
Wood glue, super glue, and basic wood working tools
Step 2: Build It
First, cut 4 11" pieces of the poplar. Glue 3 of them edge to edge, and the 4th on the end at a 90* angle. I offset the end piece by about 3/4" so that it rests on the riser. This, however, will depend on your bike, the height of the legs, and your desired angle.
Next, cut a 2" hole in the center of a piece of poplar long enough to make 2 legs. Mine are 2 3/4" tall, but play around with it to find the best height for you.
Drill 2 small holes about 2 1/2" apart, and equal distance from the center of the bottom board. This will be used to tie the piece to the riser.
Step 3: Finish It
Cut and super glue the foam sheet onto all wood parts that touch the bike. This will prevent scratching, but also helps to keep your book steady while you're riding.
Finally, run a length of paracord through the two holes with both loose ends hanging down. Rest the book holder on your bike, then use a sturdy cordlock to securely attach it to the riser.