The easiest way I could describe it would be an "H" that was much like a modified wood clamp that was mated to a "T" upper section. Straddled the top of the tire and has the T section lay against (as it were) the front side of handlebars. It did not rely on nor have to take into account which way the frame/headset was aligned. On my hybrid I was testing an adjustable feedneck in store and the mech laid it up there for me to use as a guide.