How did you insert the wedge bolt into the bar?
easy... they are made to do this.
one end of the ~ hollow tube ~ (not bar) was a bit dinged up so I used a dremel to widen the end - or flange it open slightly.
see tube label in photo: Abbreviated on the label : ALUM - TUBE (RND)
Then I placed both wedge bolts in as best as I could push them in by hand.
Placed one end on concrete and used a dead blow hammer to hammer one end then the other until they were snugly in place. I tried to rotate the bar to each end, similar to tightening lug nuts on a wheel ~ not too much of one or the other.
Then by the way they are designed I placed the washer and 3/8" nut on the bolt and tightened with a wrench. I used a channel lock "pliers" in the center of the tube where the shrink tubing would go.
I didn't really care if it was roughed up there.
The action of tightening the nut spreads the "wedge" on the bolt.
if you get a set of these and read the instructions it likely would make sense.
Hope that helps
--Ian