Cold frames are easy and affordable structures to kickstart your seedlings and plants. The minute the warm weather arrives, the frost date passes, you will be ready to get a jump on the growing season by planting strong plants in your vegetable garden.
Location, location, location. Choose a sunny area with good drainage. Placing the cold frame near a building or wind break will shelter the plants from cold spring winds. Oh yes, I know how those lovely spring breezes can change into strong cold, injuring/killing winds. A water source should be close enough that you can easily run a hose to the frames for watering the plants.
Go to your Habitat for Humanity warehouse, Good Will, your uncle's garage, or wherever you can pick up some used windows. These make excellent tops for cold frames. You can set the glass panes on top of cement blocks making sure you have a way to weight them down to weather the winds. You can also build a "frame" of wood to set the window on. The wood frame allows you to add hinges to the window and attach it to the frame so you can prop open the window allowing air to circulate through the plants.
My DH suggested using 4-6 mm vinyl stapled to a frame if you cannot locate windows. Check the nurseries and lumber companies for the vinyl.
CAUTION: On a sunny day, you must take the cover off the plants or they will bake in the cold frame box. Prop the window up with a stick, but CAUTION that the wind doesn't blow the window over and break it.
Cold frames are an inexpensive way to get a head start on your garden by hardening off the plants--acclimating them for outdoor planting. After the weather turns warm, the cold frame can be taken apart and put away until you need it next year. Best of all, when you get that itch to play in the dirt and start those seeds, you can get to it earlier by protecting the tender seedlings and plants in the cold frame.