ref: c172881606bfa194399a0b181b419a34488331d6
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