The top of the carriage bolts are square just below the heads, I pounded them into the trunk floor with a sledge hammer and they turned the round drill holes into square holes, then from underneath I fastened the bolts to the car with stainless Nylon Lock Nuts and washers. The bolts do not spin whatsoever. The wing nuts are stainless as well.
I also posted links that I ordered 2 new 3/8" x 6" Stainless Steel Bolts which should arrive in a few days. I also ordered stainless hinges, so in a couple of weeks everything will be stainless steel.
donald wrote:Very neat. But not sure I would like the idea of wing nuts in a location where they can rust. Regular grease will help, but maybe use a copper or zinc grease. Think about what might happen to the upper end of the bolts too - if the nuts slacken at the top and they, and the bolts, end up rotating when you attempt to remove the lower nuts if they are corroded/choked with dirt, then you might not be able to remove the wheel ever again - I suggest you make sure you can reach up through the spokes with a spanner [to stop the top bolts spinning] to make sure this situation couldn't happen.