I believe the metal sleeves that the bolts go into are the pins.
Edit: I probably shouldn't have said "sleeves". That has more than one meaning in this context. I'm talking about hollow pins, secured by bolts when I say "sleeves".
I think it's right. He seemed to be describing hollow pins with threaded holes. The pins hold the sections together, the bolts screw into, and steady the pins.
I believe the metal sleeves that the bolts go into are the pins.
Edit: I probably shouldn't have said "sleeves". That has more than one meaning in this context. I'm talking about hollow pins, secured by bolts when I say "sleeves".