Where does this seat belt component go?

[Roberts280Z]

I removed the seat belts 3 years ago when I started some restoration work. Now I'm trying to put them back in, and I cannot determine where this part goes:

This is a view of the lower retractor with the plastic cover removed. The unknown part is in the red box. I assume they go in the lower retractor, but I'm not even sure of that. There are two of these, and they are identical (i.e. not mirror image).

The FSM doesn't show these.  Does anybody know what these are, and where they go, or are they even needed?

 

[Zed Head]

http://www.carpartsmanual.com/datsun/Z-1969-1978/body-260z-280z/2-seater/safety-belt

[Roberts280Z]

Ah, thanks.  I saw your reply on my phone when I was outside working on the Z, and I couldn't see the part on that parts diagram  Then I tried the 'blind-man-jigsaw-puzzle' approach, and came up with this:

Then I looked at the parts diagram again on a larger screen, and indeed I see it there now:

It's some sort of shim or spacer.  I have two pieces, and they only fit the driver's side, so I suppose both pieces were installed there, with none on the passenger side.