ref: 19cc42d6b51d80fa90d08e4bfc17360508d8a627
dir: /sys/lib/troff/font/devutf/charlib/bx/
/build_bx {
pop
size 2 div /side exch def
currentpoint
newpath
moveto
0 side rlineto
side 0 rlineto
0 side neg rlineto
closepath
fill
} def