diff --git a/docs/source/usersguide/input.rst b/docs/source/usersguide/input.rst
index d98804c867..b1186874a3 100644
--- a/docs/source/usersguide/input.rst
+++ b/docs/source/usersguide/input.rst
@@ -708,6 +708,13 @@ Each ``<surface>`` element can have the following attributes or sub-elements:
 
     *Default*: None
 
+  :label:
+    An optional string label to easily identify the surface in summary 
+    output files. This string is limited to 52 characters for formatting
+    purposes.
+
+    *Default*: None
+
   :type:
     The type of the surfaces. This can be "x-plane", "y-plane", "z-plane",
     "plane", "x-cylinder", "y-cylinder", "z-cylinder", or "sphere".