Lock it or Lose it

[pistonbroke]

Hi All,, OK I searched the topic and could not find the answer. I have a NOS Hurd lock cylinder for my 41 pickup ignition. Someone has removed the original and drove a wood dowel in its place I assume to hold the lock pin up. My question is what supposed to hold the cylinder in the drop? I see a hole in the back side of the drop , it appears that something should go in it and into the side of the cylinder but what.? I see no threads in the hole. Thanks