Right, it is a cold frame to start with. I can control moisture and heat the soil faster for germination. When stuff starts coming up, I remove the glass and let them run. If a danger of frost comes up, I put the glass back on or cover with plastic. I placed 2 of them on my lateral lines a few years back and they work great. Full sun all day, facing south. It allowed me to use some of the yard that was just dedicated to grass before. And of course, due to the laterals, I could not plow and dig.
The glass is from old screen door sections I used to make a mini greenhouse years ago. I built a frame and screwed 4 doors to it. One of the extra pieces of glass made the top. I put some shelves in it and tried to use it to start seeds and plants in it early on. It never really worked like I wanted it too, so I dismantled it. Last spring, a hail storm took out several pieces of glass on the beds. I scrounged up some glass shower doors that dad bought at an auction to replace them. The lumber was from old packing crates I collected from a jobsite.