Close One End
The front end of the jig is closed in with 3/4″ inch plywood. I’ll rip to width, then cut to length.
Mark a line with a square 3/8’s from each edge. And mark the centers of each base. Drill pilot holes for screws.
Apply some glue, then a few nails to hold it in place for the screws.
For more strength attach galvanized angle brackets to each front corner using short pan head screws.
Turn the jig upside down and mark the locations for the bases on each end.
Add two screws on an angle to hold the bases in place before drilling for the carriage bolts.
I then remembered that I had a long drill bit so this went quick. You can do this step with a shorter bit but try to get the holes lined up so the bolts will tap in easily.
Repeat this process at the other end. I tapped the carriage bolts up through the inside of the jig and secured the base with a flat washer, a lock washer, and a nut.
For the other end I laid the jig over on its side on saw horses to tap in the carriage bolts.
The axle can now go in the groove and be secured with short mending plates. The cotter pins holding the wheels to the axle can now be bent over to keep them in place.
To the front base I glued and screwed on two feet made from some scrap 2×6. This makes the jig sit closer to level.