How to build a greenhouse
STEP 2. The side wall-frames
Construct all the framing out of 1 1/2" x 3 1/2" (90 mm x 45 mm) treated, or natural decay-resistant wood.
On a flat surface, make up the two side wall frames to the dimensions shown in the above drawing.
Make the diagonal measurements equal (in the same way as with the base in Step 1), and when the frame is square, cut and fix the bracing members in place. (See above drawing.)