Cut two 33 1/2" 2x4's and two 37" 2x4's. 1.5" from the end of the 33" 2x4's, drill a 3/8" hole in the center. This hole will hold a 4" long, 3/8" diam. carriage bolt. The carriage bolt has a square bit under the head so that it digs into the wood. This enables you to tighten the wing nut w/o having to hold onto the other end of the bolt. Kind of like embedding the bolt into the wood. On the other end of each of these pieces, attach one side of a 3 1/2" wide hinge. This hinge will eventually get attached to the appropriate brace on the main support.

In the 37" 2x4 you will need to cut a 1' 3" long slot which is 3/8" wide. This is the slot that the carriage bolt will slide through when you adjust the angle. I cut this slot using a jigsaw (also called a scroll saw). First, mark the beginning and end of the slot. Using a 3/8" drill bit, drill a hole at the beginning and end of the slot. This will give you a starting and ending point from which to insert the jigsaw blade. Draw an outline of the slot between each hole so you have a guide and saw out the slot. I found this a bit tough (hadn't used a jigsaw before), but as long as you don't go way outside the lines, you can always fix it up. Once you've drilled out the slot, take a 3/8" bolt and slide it through the length of it to make sure you have sufficient width along the entire length. (Those with routers already know how easy this will be for them).

Steve Baird from Australia sent in the great suggestion of clamping down another board to act as a guide for the jigsaw to ride against. He says "simply measure the distance between the blade and the edge of the base on the saw to calculate the position to clamp the guide. Don't forget to allow for the width of the saw blade. If the rear support is not wide enough then clamp another piece of timber next
to it to support your guide."

Attach another hinge to the bottom of this piece, in the same manner you did to the top piece. Leave the assembly until we've completed a few more steps.