Well, your topic and walking out to the dog sleeping on my tiny little kale seedlings finally motivated me to head out to the lumber yard and build one of my cold frame / cage contraptions. This garden bed has been a tragedy of dying seedlings. This is the 3rd time I've planted it this season. The first time the dog rolled in the fresh
compost immediately after I planted all my transplants. Oops. Then the squirrels came by the next day and ripped out the remaining struggling seedlings I had re-planted. Sigh. The second time, I didn't have automatic watering setup and my partner misjudged how much water evaporates here… fried seedlings. This third time I'm desperate to get something out of it, and I'm hopeful!
If I built this again, I'd find a better way to force the top hatch into square. Probably some diagonal braces on the ends, or maybe some tension wires running in Xs. As it is, it's slightly out of square, but good enough for me.