c2,
I just read the article (tech note). Based on the description, it sounds like a plate to extend the width of the cross-member with a thick pipe welded to it. The other piece could be a similar plate that sits inside the cavity of a floor jack with two vertical plates on each end drilled to allow a bolt to pass through each end and through the center of the pipe on the other piece. Like a hinge? I architect software better than I do tools
Great find! I may build one myself.
Tony