diff --git a/nhf/parts/handle.py b/nhf/parts/handle.py
index dc6a01f..d6b926c 100644
--- a/nhf/parts/handle.py
+++ b/nhf/parts/handle.py
@@ -73,6 +73,8 @@ class BayonetMount(Mount):
     # Angular span (in degrees) of the slider
     pin_span: float = 15
     pin_height: float = 5
+    # Wall at the bottom of the slot
+    gap: float = 3
 
     # Angular span (in degrees) of the slot
     slot_span: float = 90
@@ -80,6 +82,7 @@ class BayonetMount(Mount):
     # Number of pins equally distributed along a circle
     n_pin: int = 2
 
+
     def __post_init__(self):
         assert self.diam_outer > self.diam_inner
         assert self.n_pin * self.slot_span < 360
@@ -91,7 +94,7 @@ class BayonetMount(Mount):
         return self.diam_inner
 
     def external_thread(self, length: float):
-        assert length > self.pin_height
+        assert length > self.pin_height + self.gap
         pin = (
             Cq.Workplane('XY')
             .cylinder(
@@ -109,17 +112,18 @@ class BayonetMount(Mount):
         )
         result = (
             Cq.Workplane('XY')
+            .workplane(offset=self.gap)
             .polarArray(radius=0, startAngle=0, angle=360, count=self.n_pin)
             .eachpoint(lambda loc: pin.located(loc), combine='a')
             .clean()
         )
         return result
     def internal_thread(self, length: float):
-        assert length > self.pin_height
+        assert length > self.pin_height + self.gap
         slot = (
             Cq.Workplane('XY')
             .cylinder(
-                height=length,
+                height=length - self.gap,
                 radius=self.diam_outer / 2,
                 angle=self.pin_span,
                 centered=(True, True, False)
@@ -140,7 +144,9 @@ class BayonetMount(Mount):
                 radius=self.diam_outer / 2,
                 centered=(True, True, False),
             )
-            .polarArray(radius=0, startAngle=-self.slot_span+self.pin_span, angle=360, count=self.n_pin)
+            .copyWorkplane(Cq.Workplane('XY'))
+            .workplane(offset=self.gap)
+            .polarArray(radius=0, startAngle=self.slot_span, angle=360, count=self.n_pin)
             .cutEach(lambda loc: slot.located(loc))
             .clean()
             .copyWorkplane(Cq.Workplane('XY'))