diff --git a/ClosedXML/ClosedXML/ClosedXML/Excel/XLConstants.cs b/ClosedXML/ClosedXML/ClosedXML/Excel/XLConstants.cs
new file mode 100644
index 0000000..f01f06e
--- /dev/null
+++ b/ClosedXML/ClosedXML/ClosedXML/Excel/XLConstants.cs
@@ -0,0 +1,13 @@
+
+namespace ClosedXML.Excel
+{
+    //Use the class to store magic strings or variables.
+    internal static class XLConstants
+    {
+        internal static class Comment
+        {
+            internal const string ShapeTypeId = "#_x0000_t202";
+            internal const string AlternateShapeTypeId = "#_xssf_cell_comment";
+        }
+    }
+}