: If only the disc part could be unscrewed from the post...

the usual process would be to glue the stud to the inside of the kayak. Then you would set the rail over the studs and use nuts and washers to tighten the rail in place. Removal would be the opposite: remove the nuts and washers and the rails should just slide off the studs.

Obviously you would want to have your studs glued into the right place, and the easiest way to align them is to loosely mount them to the rail so they are in place while the glue or epoxy sets up. if you go this route you just have to be sure that the rail is greased or wrapped in saran wrap so your epoxy doesn't glue it, too.

PGJ