diff --git a/documentation/ref-manual/ref-structure.xml b/documentation/ref-manual/ref-structure.xml
index e0209c1afa..be292eb136 100644
--- a/documentation/ref-manual/ref-structure.xml
+++ b/documentation/ref-manual/ref-structure.xml
@@ -659,6 +659,22 @@
         </para>
     </section>
 
+    <section id='structure-build-tmp-sstate-control'>
+        <title><filename>build/tmp/sstate-control/</filename></title>
+
+        <para>
+            The OpenEmbedded build system uses this directory for the
+            shared state manifest files.
+            The shared state code uses these files to record the files
+            installed by each sstate task so that the files can be removed
+            when cleaning the recipe or when a newer version is about to
+            be installed.
+            The build system also uses the manifests to detect and produce
+            a warning when files from one task are overwriting those from
+            another.
+        </para>
+    </section>
+
     <section id='structure-build-tmp-sysroots'>
         <title><filename>build/tmp/sysroots/</filename></title>