Spare
Re: Spare
It’s like a boat trailer spare.
Take everything off
Put the slate n with the long bolt/threaded rod going THROUGH one of the stud holes of the wheel. Them put the plate back on. Then the spacer then the bolt. Tighten until the wheel contacts the back post and no longer feels loose.
You may want to weld a chain to the upright post to keep the tire from bouncing away.