It's basically two 8 foot long 1x2s with a bunch of cross pieces to hold the tires in place.
You can use 2x6's for the cross pieces and save yourself a bunch of time (cut a bunch of 24" long 2x6 sections, screw them in, done), but stores were closed to I used what I had around. I created a bunch of 6" long pieces of 2x3 and 2x4, and attached it to 24" long 1x6" sections. The key was just to make sure the height of the cross-pieces was at least 6", anything less and the bikes didn't want to stand up all that well.
- Tire width - they're all different, so check your bikes as you go, and adjust the spacing
- Sand the wood - you wouldn't want a splinter causing a flat
- Handlebar width - again, I put my bike in each successive slot before I set the next one to make sure the handlebars didn't overlap
- Use screws instead of nails - you might want to move some of the cross pieces to accommodate different tire widths or bike widths down the road