In principal, this rack is just a railing. The bikes are held in place by their wheels resting against the wood, with the tires keeping them from rolling. I was concerned that this design might put too much torque on the rims, and that a triangular two-touch system would be better, but this design works great, even with road race wheels.
Step 1: Tools and Materials
For the dimensions of the structure, I worked around a particular room where I wanted the parking to go. It is generally recommended that slot-type bike parking has 24" of space between each bike, from tire to tire. I wanted eight bikes to fit into a 144" space, so I narrowed it down to 17" from tire to tire. There is some handlebar overlap, but because of the generous vertical dimensions of the assemblies, you can easily lift your handlebars over other bikes that might be in your way.
Here are some general measurements to help you to customize the bike rack for your specific needs.
Each parking assembly: two posts of 1"x2"x27" (wood)
Parking base: 2"x4" (wood)
Parking top: 2"x4" (wood)
Screws: 8x 4" wood screw per assembly
Each assembly should have a gap of 2.5" between posts for the tire. If you are a downhiller and have wider tires, give yourself a little more room. From assembly to assembly, have at least a 12" space.
To fit in a 144" room, I chose a top and a base of 124", and eight parking assemblies. For the remainder of this instructable, I will be writing specifically to my project, but hopefully you can easily retrofit the design for your own needs!