diff --git a/sysrap/sn.h b/sysrap/sn.h
index f32c0a5be..c9045274c 100644
--- a/sysrap/sn.h
+++ b/sysrap/sn.h
@@ -422,6 +422,7 @@ struct SYSRAP_API sn
     **/
 
     static sn* Cylinder(double radius, double z1, double z2) ;
+    static sn* Trapezoid(double z, double y, double x, double ltx);
     static sn* Cone(double r1, double z1, double r2, double z2);
     static sn* Sphere(double radius); 
     static sn* ZSphere(double radius, double z1, double z2);
@@ -2802,6 +2803,24 @@ inline sn* sn::Cylinder(double radius, double z1, double z2) // static
     nd->setBB( -radius, -radius, z1, +radius, +radius, z2 );
     return nd ;
 }
+
+/**
+ * Support right angular wedge from STEP.
+ *
+ * References:
+ *
+ *   https://geant4-userdoc.web.cern.ch/UsersGuides/ForApplicationDeveloper/html/Detector/Geometry/geomSolids.html#constructed-solid-geometry-csg-solids
+ *   https://github.com/Geant4/geant4/blob/master/source/geometry/solids/CSG/include/G4Trap.hh
+ */
+inline sn* sn::Trapezoid(double z, double y, double x, double ltx)
+{
+    assert( x > 0 && y > 0 && z > 0 && ltx > 0 && ltx < x );
+    sn* nd = Create(CSG_TRAPEZOID);
+    nd->setPA(x, y, z, 0.f, ltx, 0.f);
+    nd->setBB(-0.5*x, -0.5*y, -0.5*z, +0.5*x, +0.5*y, +0.5*z);
+    return nd;
+}
+
 inline sn* sn::Cone(double r1, double z1, double r2, double z2)  // static
 {   
     assert( z2 > z1 );
@@ -4889,6 +4908,12 @@ inline void sn::setAABB_LeafFrame()
         assert( px == 0. && py == 0. && a == 0. ); 
         setBB( px-radius, py-radius, z1, px+radius, py+radius, z2 );   
     }
+    else if( typecode == CSG_TRAPEZOID )
+    {
+        double x, y, z, unused1, ltx, unused2;
+        getParam_(x, y, z, unused1, ltx, unused2);
+        setBB(-0.5*x, -0.5*y, -0.5*z, +0.5*x, +0.5*y, +0.5*z);
+    }
     else if( typecode == CSG_DISC )
     {
         double px, py, ir, r, z1, z2 ;
diff --git a/u4/U4Solid.h b/u4/U4Solid.h
index ac4242096..0082a19a0 100644
--- a/u4/U4Solid.h
+++ b/u4/U4Solid.h
@@ -42,6 +42,7 @@ npy/NNodeUncoincide npy/NNodeNudger
 #include "G4Ellipsoid.hh"
 #include "G4Box.hh"
 #include "G4Tubs.hh"
+#include "G4Trap.hh"
 #include "G4Polycone.hh"
 #include "G4Cons.hh"
 #include "G4Hype.hh"
@@ -67,6 +68,7 @@ enum {
     _G4Ellipsoid, 
     _G4Box,
     _G4Tubs, 
+    _G4Trap,
     _G4Polycone, 
     _G4Cons,
     _G4Hype,
@@ -85,6 +87,7 @@ struct U4Solid
     static constexpr const char* G4Ellipsoid_         = "Ell" ; 
     static constexpr const char* G4Box_               = "Box" ;
     static constexpr const char* G4Tubs_              = "Tub" ;
+    static constexpr const char* G4Trap_              = "Trp" ;
     static constexpr const char* G4Polycone_          = "Pol" ;
     static constexpr const char* G4Cons_              = "Con" ;
     static constexpr const char* G4Hype_              = "Hyp" ;
@@ -132,6 +135,7 @@ struct U4Solid
     void init_Ellipsoid(); 
     void init_Box(); 
     void init_Tubs(); 
+    void init_Trap();
     void init_Polycone(); 
     void init_Cons(); 
     void init_Hype(); 
@@ -279,6 +283,7 @@ inline int U4Solid::Type(const char* name)   // static
     if( strcmp(name, "G4Ellipsoid") == 0 )         type = _G4Ellipsoid ; 
     if( strcmp(name, "G4Box") == 0 )               type = _G4Box ; 
     if( strcmp(name, "G4Tubs") == 0 )              type = _G4Tubs ; 
+    if( strcmp(name, "G4Trap") == 0 )              type = _G4Trap ;
     if( strcmp(name, "G4Polycone") == 0 )          type = _G4Polycone ; 
     if( strcmp(name, "G4Cons") == 0 )              type = _G4Cons ; 
     if( strcmp(name, "G4Hype") == 0 )              type = _G4Hype ; 
@@ -301,6 +306,7 @@ inline const char* U4Solid::Tag(int type)   // static
         case _G4Ellipsoid:         tag = G4Ellipsoid_         ; break ;         
         case _G4Box:               tag = G4Box_               ; break ; 
         case _G4Tubs:              tag = G4Tubs_              ; break ; 
+        case _G4Trap:              tag = G4Trap_              ; break ;
         case _G4Polycone:          tag = G4Polycone_          ; break ; 
         case _G4Cons:              tag = G4Cons_              ; break ; 
         case _G4Hype:              tag = G4Hype_              ; break ; 
@@ -397,6 +403,7 @@ inline void U4Solid::init_Constituents()
         case _G4Ellipsoid         : init_Ellipsoid()             ; break ; 
         case _G4Box               : init_Box()                   ; break ; 
         case _G4Tubs              : init_Tubs()                  ; break ; 
+        case _G4Trap              : init_Trap()                  ; break ;
         case _G4Polycone          : init_Polycone()              ; break ; 
         case _G4Cons              : init_Cons()                  ; break ; 
         case _G4Hype              : init_Hype()                  ; break ; 
@@ -790,6 +797,20 @@ inline void U4Solid::init_Tubs()
 } 
 
 
+inline void U4Solid::init_Trap()
+{
+    const G4Trap* trap = dynamic_cast<const G4Trap*>(solid);
+    assert(trap);
+
+    double z   = 2*trap->GetZHalfLength()/CLHEP::mm;
+    double y   = 2*trap->GetYHalfLength1()/CLHEP::mm;
+    double x   = 2*trap->GetXHalfLength1()/CLHEP::mm;
+    double ltx = 2*trap->GetXHalfLength2()/CLHEP::mm;
+
+    root = sn::Trapezoid(z, y, x, ltx);
+}
+
+
 inline void U4Solid::init_Polycone()
 {
     const G4Polycone* polycone = dynamic_cast<const G4Polycone*>(solid);