Use a router to make a rabbet cut 2 inches into each 4-inch end, 1 inch deep, on the 2-inch by 4-inch by 68-inch lengths of stock lumber. A rabbet is a rectangular recess along the edge or end of a work piece. Refer to the diagram that accompanies this step to make the cut correctly.
Make a 4-inch long by 2-inch deep by 1-inch high rabbet cut flush with each end of the 2-inch by 4-inch by 36-inch lengths of stock lumber, coming in from the long side. Refer to the diagram that accompanies this step to make the cut correctly.
Lay the 68-inch long pieces rabbet side down into the corresponding rabbet cuts in the 36-inch long pieces. Drill 1/4-inch diameter pilot holes in the positions indicated in the diagram that accompanies this step. Countersink all holes. Secure all pieces together using 1 1/2-inch long brass wood screws.
Place 4-inch by 4-inch posts flush with all four corners. Position the remaining two posts midway along the long sides of the bed, flush with the frame. Drill 1/4-inch diameter pilot holes in the positions indicated in the diagram that accompanies this step. Secure the posts to the bed frame using 4-inch long, 1/2-inch diameter brass wood screws.
Attach the four sides of the bed to the platform, flush with the top edge, using 1 1/2-inch long, 1/2-inch diameter brass wood screws. Place the 72-inch by 38-inch by 1-inch thick plywood sheet on top of the frame. Drill pilot holes beginning in the corners, every 6 inches around the perimeter of the platform, 1 1/2-inches from the edge. Countersink all holes. Secure the platform to the frame using 1 1/2-inch long, 1/2-inch diameter brass wood screws.
Use a belt sander with coarse, medium, fine, and extra fine belts in that order, to sand the entire bed smooth. Apply 3 to 4 coats of clear acrylic wood treatment, drying 24 hours between coats.
Fold each end of the 7-foot long, 3-foot wide length of Kelly green broadcloth sheets over 1 inch. Run a double line of stitches, 3/4-inch from the fold. Fold each end over again, 5 inches and repeat the double seam. This makes a casing for the 3 feet long PVC pipes. Insert the 3-foot long, 1 15/16-inch diameter PVC pipes through each end of the Kelly green fabric.
Apply PVC cement to the last 2 inches of the outside of each end of the 6 feet long, 1 15/16-inch diameter lengths of PVC pipe. Insert into one side of a 2-inch diameter, 3-way PVC connector.
Repeat Step One for the last 2 inches of the outside of each end of four of the the 3 foot long, 1 15/16-inch diameter lengths of PVC pipe. All open ends of the connectors should be facing up when the 3-feet by 6-feet PVC frame is laid on the floor.
Apply PVC cement to the last two inches of the outside of the 18-inch long, 1 15/16-inch diameter PVC pipes. Insert them into each 3-way connector. Apply PVC cement to the insides of the last inch of each leg, and then insert PVC caps. You now have two tractor sides.
Fold one end of the 10-foot long, 3-foot wide length of Kelly green broadcloth sheet over 1 inch. Run a double line of stitches 3/4-inch from the fold. Fold the end over again 5 inches and repeat the double seam. This makes a casing for the first 3-foot long PVC pipe of the tractor roof. Insert one 3-foot long, 1 15/16-inch diameter PVC pipe through the end of the 10-foot long Kelly green fabric.
Assemble the 3 foot by 3 foot tractor roof frame using three-way PVC connectors, PVC cement, the remaining pieces of 36-inch long, 1 15/16-inch diameter PVC and the 4-foot long legs. Apply PVC cement to the outside of the rear PVC pipe.
Drape the 10 feet long fabric over the rear PVC pipe, leaving the bottom edge loose. Press the fabric into the PVC cement to make a smooth seal. Tighten the 1 1/2-inch long, 1/2-inch diameter brass wood screws through holes in the 2-inch wide, 8-inch long plastic strips to secure the legs to the sides of the bed.
Sew covers from black broadcloth for the 18-inch round and 36-inch round foam pillow forms to make tractor wheel pillows. Attach to the sides of the tractor frame using plastic loop fabric strips. Sew a yellow cover for the 6-inch by 3-foot by 18-inch rectangular pillow form to make the hay bale pillow.