The side Co2 not Co2 thingy.
The ends go into the axe. The tope one seems to go straight into the axe.
The bottom one seems to go into something and that something is in the axe.
Any idea what it is?
Yeah, it's kind of a little tapered knob thingy. I had a thought of what to use for that years ago, but it's been so long since I've read through this thread, or even looked at my axe parts, I don't really recall much about it. But yes, there is something there. (wow, this post added nothing. :lol ) I think some one said they used a cap off of a pin or something like that. I would suggest looking through the droors at the doohicky section of any hard ware store, or the plumbing section.