+ show z4r; show z4l;
+ addto currentpicture also currentpicture
+ shifted (-x4r,0) xscaled -1 shifted (x4l,0);
+
+enddef;
+
+save uitsteek;
+ uitsteek = .25;
+def draw_ledger(expr wid)=
+ set_char_box(uitsteek * wid, (1+ uitsteek)*wid,
+ ledgerlinethickness#/2,ledgerlinethickness#/2);
+ pickup pencircle scaled ledgerlinethickness;
+ rt x2 = w;
+ lft x1 = -b;
+ y1 = y2 = 0;
+ draw z1 .. z2;