I've never actually had a cold frame. I did build a 50' long hoop greenhouse once, but haven't tried using a cold frame to extend the growing season.
Our new house has a roughly 25' wide south facing wall on the outside of our attached garage. It gets a lot of sun. I wanted to have a lean-to greenhouse, but it is within 12' or so of the property line, and I doubt I could get away with the greenhouse. A small row of cold frames, on the other hand, might work out.
Can anyone give me some ideas on materials to use? I'm thinking of using wood and polycarbonate panels, and perhaps insulating the inside of the wood - or would the outside be better? I'd like them to be several feet deep. Even just standing next to that wall outside on a cold but windless day, you can feel quite warm.