diff --git a/STL_Extension/doc/STL_Extension/Concepts/Hashable.h b/STL_Extension/doc/STL_Extension/Concepts/Hashable.h
new file mode 100644
index 00000000000..1b0df458143
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+++ b/STL_Extension/doc/STL_Extension/Concepts/Hashable.h
@@ -0,0 +1,23 @@
+
+/*!
+\ingroup PkgStlExtensionConcepts
+\cgalConcept
+
+A type `Key` is a model of the concept `Hashable` if the
+specializations `boost::hash<Key>` and `std::hash<Key>` exist. 
+
+\cgalHasModel All handles and indices of \cgal data structures.
+
+
+\sa `CGAL::Unique_hash_map<Key,Data,Hash>` 
+\sa `std::unordered_set`
+\sa `std::unordered_map`
+\sa `boost::unordered_set`
+\sa `boost::unordered_map`
+
+*/
+
+class Hashable {
+
+};
+