diff --git a/mcstas-comps/contrib/Monochromator_2foc.comp b/mcstas-comps/contrib/Monochromator_2foc.comp
index 5fdcb60f7..9013ecf5c 100644
--- a/mcstas-comps/contrib/Monochromator_2foc.comp
+++ b/mcstas-comps/contrib/Monochromator_2foc.comp
@@ -321,8 +321,7 @@ MCDISPLAY
         yt = 0;
         yt1 = 0;
       }
-      multiline (5, xt + yt, (double)ymin, (double)zmin, xt + yt1, (double)ymax, (double)zmin, xt1 + yt1, (double)ymax, (double)zmax, xt1 + yt, (double)ymin,
-                 (double)zmax, xt + yt, (double)ymin, (double)zmin);
+      polygon (4, xt + yt, (double)ymin, (double)zmin, xt + yt1, (double)ymax, (double)zmin, xt1 + yt1, (double)ymax, (double)zmax, xt1 + yt, (double)ymin, (double)zmax);
     }
   }
 %}
diff --git a/mcstas-comps/contrib/Monochromator_bent.comp b/mcstas-comps/contrib/Monochromator_bent.comp
index 9a1e12a30..72bf0bcbe 100755
--- a/mcstas-comps/contrib/Monochromator_bent.comp
+++ b/mcstas-comps/contrib/Monochromator_bent.comp
@@ -1640,19 +1640,16 @@ MCDISPLAY
       // These 8 coordinates define 8 points. Coordinate transform these
       // to the current crystal
       rotate_all_points (&x_inner[0], &x_outer[0], &x_inner[1], &x_outer[1], &y_top, &y_bottom, &z_inner[0], &z_outer[0], &z_inner[1], &z_outer[1], points, mono);
-      // Draw a box in th xy plane
-      multiline (5, points[0][0], points[0][1], points[0][2], points[2][0], points[2][1], points[2][2], points[3][0], points[3][1], points[3][2], points[1][0],
-                 points[1][1], points[1][2], points[0][0], points[0][1], points[0][2]);
-
-      // Draw curving parts of crystal in the zx plane
-      line (points[0][0], points[0][1], points[0][2], points[4][0], points[4][1], points[4][2]);
-      line (points[1][0], points[1][1], points[1][2], points[5][0], points[5][1], points[5][2]);
-      line (points[2][0], points[2][1], points[2][2], points[6][0], points[6][1], points[6][2]);
-      line (points[3][0], points[3][1], points[3][2], points[7][0], points[7][1], points[7][2]);
+      // Start cap, then inner, outer, top and bottom faces of this segment
+      if (i == 0)
+        polygon (4, points[0][0], points[0][1], points[0][2], points[2][0], points[2][1], points[2][2], points[3][0], points[3][1], points[3][2], points[1][0], points[1][1], points[1][2]);
+      polygon (4, points[0][0], points[0][1], points[0][2], points[1][0], points[1][1], points[1][2], points[5][0], points[5][1], points[5][2], points[4][0], points[4][1], points[4][2]);
+      polygon (4, points[2][0], points[2][1], points[2][2], points[3][0], points[3][1], points[3][2], points[7][0], points[7][1], points[7][2], points[6][0], points[6][1], points[6][2]);
+      polygon (4, points[0][0], points[0][1], points[0][2], points[2][0], points[2][1], points[2][2], points[6][0], points[6][1], points[6][2], points[4][0], points[4][1], points[4][2]);
+      polygon (4, points[1][0], points[1][1], points[1][2], points[3][0], points[3][1], points[3][2], points[7][0], points[7][1], points[7][2], points[5][0], points[5][1], points[5][2]);
     }
-    // Draw a final box in the xy plane
-    multiline (5, points[4][0], points[4][1], points[4][2], points[6][0], points[6][1], points[6][2], points[7][0], points[7][1], points[7][2], points[5][0],
-               points[5][1], points[5][2], points[4][0], points[4][1], points[4][2]);
+    // End cap
+    polygon (4, points[4][0], points[4][1], points[4][2], points[6][0], points[6][1], points[6][2], points[7][0], points[7][1], points[7][2], points[5][0], points[5][1], points[5][2]);
   }
 
   // line(0,0,0,
diff --git a/mcstas-comps/contrib/Monochromator_bent_complex.comp b/mcstas-comps/contrib/Monochromator_bent_complex.comp
index 4cee0f1fa..1d9af0ae6 100755
--- a/mcstas-comps/contrib/Monochromator_bent_complex.comp
+++ b/mcstas-comps/contrib/Monochromator_bent_complex.comp
@@ -341,19 +341,16 @@ MCDISPLAY
       // These 8 coordinates define 8 points. Coordinate transform these
       // to the current crystal
       rotate_all_points (&x_inner[0], &x_outer[0], &x_inner[1], &x_outer[1], &y_top, &y_bottom, &z_inner[0], &z_outer[0], &z_inner[1], &z_outer[1], points, mono);
-      // Draw a box in th xy plane
-      multiline (5, points[0][0], points[0][1], points[0][2], points[2][0], points[2][1], points[2][2], points[3][0], points[3][1], points[3][2], points[1][0],
-                 points[1][1], points[1][2], points[0][0], points[0][1], points[0][2]);
-
-      // Draw curving parts of crystal in the zx plane
-      line (points[0][0], points[0][1], points[0][2], points[4][0], points[4][1], points[4][2]);
-      line (points[1][0], points[1][1], points[1][2], points[5][0], points[5][1], points[5][2]);
-      line (points[2][0], points[2][1], points[2][2], points[6][0], points[6][1], points[6][2]);
-      line (points[3][0], points[3][1], points[3][2], points[7][0], points[7][1], points[7][2]);
+      // Start cap, then inner, outer, top and bottom faces of this segment
+      if (i == 0)
+        polygon (4, points[0][0], points[0][1], points[0][2], points[2][0], points[2][1], points[2][2], points[3][0], points[3][1], points[3][2], points[1][0], points[1][1], points[1][2]);
+      polygon (4, points[0][0], points[0][1], points[0][2], points[1][0], points[1][1], points[1][2], points[5][0], points[5][1], points[5][2], points[4][0], points[4][1], points[4][2]);
+      polygon (4, points[2][0], points[2][1], points[2][2], points[3][0], points[3][1], points[3][2], points[7][0], points[7][1], points[7][2], points[6][0], points[6][1], points[6][2]);
+      polygon (4, points[0][0], points[0][1], points[0][2], points[2][0], points[2][1], points[2][2], points[6][0], points[6][1], points[6][2], points[4][0], points[4][1], points[4][2]);
+      polygon (4, points[1][0], points[1][1], points[1][2], points[3][0], points[3][1], points[3][2], points[7][0], points[7][1], points[7][2], points[5][0], points[5][1], points[5][2]);
     }
-    // Draw a final box in the xy plane
-    multiline (5, points[4][0], points[4][1], points[4][2], points[6][0], points[6][1], points[6][2], points[7][0], points[7][1], points[7][2], points[5][0],
-               points[5][1], points[5][2], points[4][0], points[4][1], points[4][2]);
+    // End cap
+    polygon (4, points[4][0], points[4][1], points[4][2], points[6][0], points[6][1], points[6][2], points[7][0], points[7][1], points[7][2], points[5][0], points[5][1], points[5][2]);
   }
 
   // line(0,0,0,
diff --git a/mcstas-comps/optics/Monochromator_curved.comp b/mcstas-comps/optics/Monochromator_curved.comp
index ca915a02a..caa4d51ea 100644
--- a/mcstas-comps/optics/Monochromator_curved.comp
+++ b/mcstas-comps/optics/Monochromator_curved.comp
@@ -531,8 +531,7 @@ MCDISPLAY
         yt = -(ymax * ymax - ymin * ymin) / RV / 2;
       else
         yt = 0;
-      multiline (5, xt + yt, (double)ymin, (double)zmin, xt - yt, (double)ymax, (double)zmin, -xt - yt, (double)ymax, (double)zmax, -xt + yt, (double)ymin,
-                 (double)zmax, xt + yt, (double)ymin, (double)zmin);
+      polygon (4, xt + yt, (double)ymin, (double)zmin, xt - yt, (double)ymax, (double)zmin, -xt - yt, (double)ymax, (double)zmax, -xt + yt, (double)ymin, (double)zmax);
     }
   }
 %}
diff --git a/mcstas-comps/optics/Monochromator_flat.comp b/mcstas-comps/optics/Monochromator_flat.comp
index 9bcf77bb5..636d817c3 100644
--- a/mcstas-comps/optics/Monochromator_flat.comp
+++ b/mcstas-comps/optics/Monochromator_flat.comp
@@ -251,8 +251,7 @@ TRACE
 MCDISPLAY
 %{
 
-  multiline (5, 0.0, (double)ymin, (double)zmin, 0.0, (double)ymax, (double)zmin, 0.0, (double)ymax, (double)zmax, 0.0, (double)ymin, (double)zmax, 0.0,
-             (double)ymin, (double)zmin);
+  polygon (4, 0.0, (double)ymin, (double)zmin, 0.0, (double)ymax, (double)zmin, 0.0, (double)ymax, (double)zmax, 0.0, (double)ymin, (double)zmax);
 %}
 
 END
diff --git a/mcstas-comps/optics/Monochromator_pol.comp b/mcstas-comps/optics/Monochromator_pol.comp
index e9bba3789..eb28cd251 100644
--- a/mcstas-comps/optics/Monochromator_pol.comp
+++ b/mcstas-comps/optics/Monochromator_pol.comp
@@ -200,7 +200,7 @@ TRACE
 MCDISPLAY
 %{
 
-  rectangle ("yz", 0, 0, 0, zwidth, yheight);
+  polygon (4, 0.0, -yheight / 2, -zwidth / 2, 0.0, -yheight / 2, zwidth / 2, 0.0, yheight / 2, zwidth / 2, 0.0, yheight / 2, -zwidth / 2);
   %}
 
 END