Hi, Currently, if I have one custom geometry and a few further derived custom geometries, I need to do trait register on all of them. Like: class derived_point1 : public base_point {}; class derived_point2 : public base_point1 {}; namespace boost { namespace polygon { struct geometry_concept { typedef point_concept type; }; struct geometry_concept { typedef point_concept type; }; struct geometry_concept { typedef point_concept type; }; } What I want is to register all custom geometries in one step. Like: template<typename T> struct geometry_concept()>::type> { typedef point_concept type; }; To do that, I need to add a dummy template type to all the trait classes to enable SFINAE. Attached is the patch (based on boost 1.57.0_1). Is this something we can consider? Thanks, Leo Xue