ref: 7f3cb2a9c5b740dc86c4ac4e3d4cb45bb2e69dac
dir: /sys/lib/troff/font/devutf/charlib/sq/
/build_sq {
pop
size 2 div /side exch def
currentpoint
newpath
moveto
0 side rlineto
side 0 rlineto
0 side neg rlineto
closepath
font B eq {fill} {stroke} ifelse
} def