diff --git a/nhf/touhou/yasaka_kanako/onbashira.py b/nhf/touhou/yasaka_kanako/onbashira.py
index 8f219e2..a576050 100644
--- a/nhf/touhou/yasaka_kanako/onbashira.py
+++ b/nhf/touhou/yasaka_kanako/onbashira.py
@@ -22,7 +22,7 @@ class Onbashira(Model):
     side_thickness: float = 25.4 / 8
 
     # Joints between two sets of side panels
-    angle_joint_thickness: float = 10.0
+    angle_joint_thickness: float = 15.0
     # Z-axis size of each angle joint
     angle_joint_depth: float = 60.0
     # Gap of each angle joint to connect the outside to the inside
@@ -37,6 +37,9 @@ class Onbashira(Model):
     ])
     angle_joint_flange_thickness: float = 7.8
     angle_joint_flange_radius: float = 40.0
+    angle_joint_conn_thickness: float = 6.0
+    angle_joint_conn_depth: float = 20.0
+    angle_joint_conn_width: float = 20.0
 
     # Dimensions of gun barrels
     barrel_diam: float = 25.4 * 1.5
@@ -77,6 +80,8 @@ class Onbashira(Model):
 
         for (x, y) in self.angle_joint_bolt_position:
             assert y < self.angle_joint_depth / 2
+        assert self.angle_joint_depth / 2 > self.angle_joint_conn_depth
+        assert self.angle_joint_thickness > self.angle_joint_conn_thickness
 
     @property
     def angle_side(self) -> float:
@@ -403,6 +408,23 @@ class Onbashira(Model):
             .extrude(self.angle_joint_depth*4)
             .translate((0, 0, -self.angle_joint_depth*2))
         )
+        # The mating structure
+        z1 = self.bulk_radius + (self.angle_joint_thickness - self.angle_joint_conn_thickness) / 2
+        z2 = z1 + self.angle_joint_conn_thickness
+        mating1n = (
+            Cq.Workplane()
+            .sketch()
+            .polygon([
+                (z1, 0),
+                (z1, self.angle_joint_conn_width),
+                (z2, self.angle_joint_conn_width),
+                (z2, 0),
+            ])
+            .finalize()
+            .extrude(self.angle_joint_conn_depth)
+        )
+        mating1p = mating1n.rotate((0,0,0), (1,0,0), 180)
+        angle = 360 / self.n_side
         result = (
             Cq.Workplane()
             .placeSketch(sketch)
@@ -411,6 +433,10 @@ class Onbashira(Model):
             .cut(slot.translate((0, 0, self.angle_joint_gap/2)))
             .cut(slot.translate((0, 0, -self.angle_joint_depth-self.angle_joint_gap/2)))
             .intersect(intersector)
+            .cut(mating1n)
+            .union(mating1p)
+            .union(mating1n.rotate((0,0,0),(0,0,1),angle))
+            .cut(mating1p.rotate((0,0,0),(0,0,1),angle))
         )
         h = self.bulk_radius + self.angle_joint_thickness
         hole_negative = Cq.Solid.makeCylinder(