The indexing jig is used to locate holes for bracket shoes based on the position of notches in the tension hoop.
The indexing jig is made in two parts. One part holds the indexing pin which interfaces with the tension hoop notches and a second part that holds the striking pin. Construction of the indexing jig is made simpler because the basic parts, the bases and cubes that sit on top of the bases are interchangeable except for a couple of details.
The striking pin jig does not have a threaded hole at the top of the cube. The purpose of the threaded hole is to hold the indexing pin in place. The striking pin is meant to move freely through the cube and so does not need to be held in place.
The other difference is in the counterbores as seen from the bottom of the two bases. The two bases sit in mirror image to one another and therefore the counterbores must be made with the "handedness" in mind.
NOTE: The height at which the pins are placed may vary according to your lathe. They should interface with the rim across the diameter of the rim.
The following illustration is an exploded view of the indexing pin jig. The striking pin jig is virtually a mirror image of the indexing pin jig except that it lacks the set screw and set screw threaded hole.