The 1/4" aluminum rods for the antenna are tapped at each end for threaded couplers.
There are three rods - a base section that can be pushed into the ground or held with some other mount plus two sections that go between the feedpoint and loading coil.
The base rod is threaded only on the top end, and is just cut flat (and rounded a bit with a file) on the other. This will screw into the feedpoint assembly. The first upper rod has threaded couplers attached on each end. The second, higher upper rod has open threads on one end and a coupler on the other. These attach together and connect between the feedpoint assembly and loading coil.
Cutting the threads on the rod is an interesting task. I have to admit I didn't do a perfect job and thus the antenna doesn't assemble perfectly straight. In any case, use a vise to hold the rod and any jigs, holders, etc you can rig that will help you get the die centered and flat as possible when cutting the threads.