I'm a lazy maker. I will live with problems for a long time, waiting until I stumble on the simplest, cheapest solution I can imagine. I find that I often end up with elegant, low-tech fixes that are easy to make as well as easy to live with.
A recent problem that waited a good long time for a solution was my bicycle-littered porch. My wife and I agreed that we needed a rack to organize a family stable of bikes that numbers between 4 and 7, depending on what's being built at the time (I regularly build or fix bikes for friends and local folks-in-need). For my rack, I imagined all sorts of constructions, but didn't really have the energy to cut and assemble. Like I said: I'm a lazy maker.
The solution I finally hit on was so simple as to be ridiculous: two wooden pallets leaned against each other. It's so simple that it's hardly worth saying a word about it; the picture ought to be enough. But following are a few thoughts ...
Step 1: Simple Pallet Bike Rack
These two pallets, salvaged from a dumpster, are slightly different, in ways that make a difference for the project. The one with thinner boards will be the upright pallet, as its narrower slots will hold bike wheels better. The other pallet will go upside-down, for reasons that will be clear in the next step ...
Step 2: Simple Pallet Bike Rack
For the pallet that sits on the ground, you'll want a little more wiggle-room for lining up the wheels to fit in the vertical slats. You'll do this by setting it boards-down. As you can see, this provides a 'well' for the wheels, and provides a cross-brace to serve as a stop, keeping the wheel from rolling out of place. Note in the third pic, the distance from the wall in the bottom pallet -- this provides the right angle for the top pallet to lean against the wall (remember, we're not screwing anything down ... that would be too much work).