diff --git a/nhf/touhou/shiki_eiki/crown.py b/nhf/touhou/shiki_eiki/crown.py
index 6bc3ab6..4c4c219 100644
--- a/nhf/touhou/shiki_eiki/crown.py
+++ b/nhf/touhou/shiki_eiki/crown.py
@@ -11,21 +11,27 @@ class Crown(Model):
     facets: int = 5
     # Lower circumference
     base_circ: float = 538.0
-    # Upper circumference
+    # Upper circumference, at the middle
     tilt_circ: float = 640.0
+    # Total height
     height: float = 120.0
 
     margin: float = 10.0
 
     thickness: float = 0.4 # 26 Gauge
+    side_guard_thickness: float = 15.0
+    side_guard_channel_radius: float = 90
+    side_guard_channel_height: float = 10
 
     material: Material = Material.METAL_BRASS
+    material_side: Material = Material.PLASTIC_PLA
 
     def __post_init__(self):
         super().__init__(name="crown")
 
         assert self.tilt_circ > self.base_circ
         assert self.facet_width_upper / 2 > self.height / 2, "Top angle must be > 90 degrees"
+        assert self.side_guard_channel_radius > self.radius_lower
 
     @property
     def facet_width_lower(self):
@@ -33,6 +39,15 @@ class Crown(Model):
     @property
     def facet_width_upper(self):
         return self.tilt_circ / self.facets
+    @property
+    def radius_lower(self):
+        return self.base_circ / (2 * math.pi)
+    @property
+    def radius_middle(self):
+        return self.tilt_circ / (2 * math.pi)
+    @property
+    def radius_upper(self):
+        return (self.tilt_circ + (self.tilt_circ - self.base_circ)) / (2 * math.pi)
 
     def profile_base(self) -> Cq.Sketch:
         # Generate the pentagonal shape
@@ -342,16 +357,61 @@ class Crown(Model):
         return sketch.assemble()
 
     def side_guard(self) -> Cq.Workplane:
-        rb = self.base_circ / (2 * math.pi)
-        rt = self.tilt_circ / (2 * math.pi)
+        angle = 360 / 5
         outer = Cq.Solid.makeCone(
-            radius1=rb,
-            radius2=rt,
+            radius1=self.radius_lower + self.side_guard_thickness,
+            radius2=self.radius_upper + self.side_guard_thickness,
             height=self.height,
+            angleDegrees=angle,
         )
-        return outer
+        inner = Cq.Solid.makeCone(
+            radius1=self.radius_lower,
+            radius2=self.radius_upper,
+            height=self.height,
+            angleDegrees=angle,
+        )
+        shell = (
+            outer.cut(inner)
+            .rotate((0,0,0), (0,0,1), -angle/2)
+        )
+        dx = math.sin(math.radians(angle / 2)) * self.radius_middle
+        profile = (
+            Cq.Workplane('YZ')
+            .polyline([
+                (0, self.height),
+                (-dx, self.height / 2),
+                (-dx, 0),
+                (dx, 0),
+                (dx, self.height / 2),
+            ])
+            .close()
+            .extrude(self.radius_upper + self.side_guard_thickness)
+            .val()
+        )
+        channel = (
+            Cq.Solid.makeCylinder(
+                radius=self.side_guard_channel_radius + 1.0,
+                height=self.side_guard_channel_height,
+            ) - Cq.Solid.makeCylinder(
+                radius=self.side_guard_channel_radius,
+                height=self.side_guard_channel_height,
+            )
+        )
+        return shell * profile - channel
 
     def assembly(self) -> Cq.Assembly:
+        side_guard = self.side_guard()
+        a = Cq.Assembly()
+        for i in range(1,5):
+            a = a.addS(
+                side_guard,
+                name=f"side-{i}",
+                material=self.material_side,
+                loc=Cq.Location(rz=i*360/5)
+            )
+        return a
+
+    def old_assembly(self) -> Cq.Assembly:
         front = (
             Cq.Workplane('XY')
             .placeSketch(self.profile_front())