The static_binding doc: http://steven_watanabe.users.sourceforge.net/type_erasure/libs/type_erasure/... contains: Description Represents a mapping from placeholders to the actual types that they bind to. However, the doc for: template < typename Concept2 , typename Tag2 , typename Map > any ( const any< Concept2, Tag2 > & other , const static_binding< Map > & binding ); here: http://steven_watanabe.users.sourceforge.net/type_erasure/libs/type_erasure/... contains: Requires: [snip] Map must be an MPL map with keys for all the placeholders used by Concept and values for the corresponding placeholders in Concept2. So the static_binding doc should contain something like: Represents a mapping from placeholders to the actual types that they bind to or a mapping from placeholders to placeholders, depending on where static_binding is used. HTH. -regards, Larry