The nice thing about this cold frame is that it goes together quickly and also breaks down and stores when not in use.
Although the plan below shows the dimensions, these can be adapted to suit your own needs, depending on how much space you have in your garden and what you'll be growing in it. If you overwinter tender shrubs, you'll need a larger one than if you just get an early start on vegetable seedlings. Measuring your seed-starting trays before you start to make sure the cold frame fits your equipment.

After you have determined the cold frame's final size, mark out and cut two side pieces (A), a back piece (B) and a front piece (C).

Cut the plywood to fit, making sure that the interlocking slits were cut to the thickness of the plywood plus 1/8 inch so they slide together easily (see illustration).

For lasting protection you can either paint or varnish the wood to seal it. If the frame is to be used for seedlings, it is a good idea to paint the inside faces with white paint to ensure that the light penetration is even. Alternatively, line the inside with aluminium kitchen foil.