Easy project. Just some 1018 steel, two cap screws, 4 set screws, two small bearings, and a chunk of aluminum.
Great tool for a quick centering aid. After centering with the "bump" I check it with the indicator and it is usually quite close, just a bit more tweeking and it is good to go. I made up 3 dovetail tool holders and left them un-drilled. When I know what I want to use the tool holder for I drill it as necessary. Nice to have a couple of blank QCTP holders on hand.