diff --git a/nhf/touhou/yasaka_kanako/onbashira.py b/nhf/touhou/yasaka_kanako/onbashira.py
index f423b9b..bb0b797 100644
--- a/nhf/touhou/yasaka_kanako/onbashira.py
+++ b/nhf/touhou/yasaka_kanako/onbashira.py
@@ -265,6 +265,8 @@ class Onbashira(Model):
 
     chamber_side_length: float = 400.0
     chamber_side_width_ex: float = 20.0
+    # Circular hole to hold a switch
+    chamber_front_switch_diam: float = 20.0
 
     # Dimensions of gun barrels
     barrel_diam: float = 25.4 * 1.5
@@ -1664,14 +1666,21 @@ class Onbashira(Model):
         """
         l = self.side_width
         h = self.side_width
-        h2 = 15
+        gap = 20
         return (
             self.profile_chamber_back()
             .reset()
             .rect(l, h, mode="s")
+            .push([
+                (l/2 + gap + self.chamber_front_switch_diam/2, 0)
+            ])
+            .circle(self.chamber_front_switch_diam/2, mode="s")
             .reset()
-            .push([(0, h/2 + h2)])
-            .rect(l/2, h2, mode="s")
+            .push([
+                (0, h/2 + gap),
+                (0, -h/2 - gap),
+            ])
+            .rect(l/4, gap, mode="s")
         )
     def chamber_front(self) -> Cq.Sketch:
         sketch = self.profile_chamber_front()