diff --git a/curve/PolyLine2d.cs b/curve/PolyLine2d.cs
index 5ff1aac5..a0d201e5 100644
--- a/curve/PolyLine2d.cs
+++ b/curve/PolyLine2d.cs
@@ -340,6 +340,43 @@ public PolyLine2d Transform(ITransform2 xform)
         }
 
 
+
+        static public PolyLine2d MakeBoxSpiral(Vector2d center, double len, double spacing)
+        {
+            double d = spacing / 2;
+            PolyLine2d pline = new PolyLine2d();
+            pline.AppendVertex(center);
+
+            Vector2d c = center;
+            c.x += spacing / 2;
+            pline.AppendVertex(c);
+            c.y += spacing;
+            pline.AppendVertex(c);
+            double accum = spacing / 2 + spacing;
+
+            double w = spacing / 2;
+            double h = spacing;
+
+            double sign = -1.0;
+            while (accum < len) {
+                w += spacing;
+                c.x += sign * w;
+                pline.AppendVertex(c);
+                accum += w;
+
+                h += spacing;
+                c.y += sign * h;
+                pline.AppendVertex(c);
+                accum += h;
+
+                sign *= -1.0;
+            }
+
+            return pline;
+        }
+
+
+
     }
 
 
diff --git a/mesh/MeshEditor.cs b/mesh/MeshEditor.cs
index 117d744b..8f201332 100644
--- a/mesh/MeshEditor.cs
+++ b/mesh/MeshEditor.cs
@@ -246,10 +246,10 @@ public virtual int[] StitchUnorderedEdges(List<Index2i> EdgePairs, int group_id
         /// vertex ordering must reslut in appropriate orientation (which is...??)
         /// [TODO] check and fail on bad orientation
         /// </summary>
-        public virtual int[] StitchSpan(int[] vspan1, int[] vspan2, int group_id = -1)
+        public virtual int[] StitchSpan(IList<int> vspan1, IList<int> vspan2, int group_id = -1)
         {
-            int N = vspan1.Length;
-            if (N != vspan2.Length)
+            int N = vspan1.Count;
+            if (N != vspan2.Count)
                 throw new Exception("MeshEditor.StitchSpan: spans are not the same length!!");
             N--;