Howdy, thanks in advance for any insight you can provide.
Where the shackle attaches to the holding bracket for the rear leaf springs there is a piece of steel bent at a right angle. It has two sides approximately 1"+2" and is about half an inch wide. It is attachedf to the bracket/shackle bolt just behind the nut.
I didn't get one with my Dorman replacement shackle, and I am just wondering what they do, whether I should put them back on or source a newer one - thx

 

Is this what you bought?

https://www.google.com/search?q=ford...1763708,pvt:hg

 

That helps keep the nut from spinning. When you tighten the bolt, that right angle piece will press against the shackle hanger and keep the nut from spinning, allowing you to only need to tighten the bolt side with a ratchet.