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.