The TicMarkLength is given in pixels and is 10 pixels by default. If you assign zero to the length, then the tic mark is reduced to a single point, but you can still label the marks with the TicMarkLabel property.
On assignment, the built-in EdgeTicMarksAsMcLines (the default one accessed as the EdgeTicMarksAsMcLines property) is automatically updated with the new tic mark length, but sub-set McLines created by passing a selector to EdgeTicMarksAsMcLines are not automatically updated.
TicMarkLength Property
