They are almost a commodity. For decades I have used Saris or other brand fork mounts in various vehicles. Usually I attached to to a piece of plywood, but sometimes attached to a 2 X 4 or even directly to the bed of my old pick up truck. My go-to attachment method is to buy T-nuts from the hardware store so my mounting board will lie flat. The first fork mounts that I ever used were home made but the commercial ones are so cheap that it isn't worth it to me to make my own anymore.
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My greatest fear is all of my kids standing around my coffin and talking about "how sensible" dad was.