They stored the bayonet inside the lug, back to front. You could pull it out, flip it, and slide it into the same hole pointy-end-forward.

You could disengage the connection from the back of the bayonet when it was stored, or from the front when it was deployed.

Which made every bayonet a male-male connector for two rifles. And since it was now in both the stored AND deployed positions, the only way to remove it was to drill a hole into the gun.