ref: cbe4b116989c0bfec49b9ae7a1d9a85ead6648ae
dir: /sys/lib/troff/font/devutf/charlib/RC/
/build_RC { pop size 4 div /side exch def currentpoint newpath moveto 0 side 1.5 mul rmoveto 0 side rlineto side 2.5 mul 0 rlineto 0 side neg rlineto closepath fill } def