Here's one simple jig that does the work of two. Use it to locate the center of round stock, or use the increment holes to mark different sizes of circles and arcs.
I love the tenoning jig that appeared in the June 1997 issue. But, when I couldn't find a local supplier for the plastic knobs, I built a knob using scrap birch and a 3/8" T-nut. Here's how: