\def\finishbar#1{\rightalign{\thinbar{#1}\kern\smallspace\thickbar{#1}}}
\def\fatdoublebar#1{\hbox{\phantom{\repeatcolon\kern2\smallspace}\thickbar{#1}\kern\smallspace\thickbar{#1}}}
-
+\def\extender#1{\vrule width#1 height .8\stafflinethickness}
% ugh
% see e.g. input/test/beam-pos.ly