Fender Attachment

[Payne Family Computer]

Good day all I was watching Chop Cut Rebuild and they were working on a 41 Willies. They had the front fenders off and were installing an attachment that would allow easy removal and adjustment of the fender. I have the front fender off my 1966 Barracuda for body work.It looked like a plug that was bolted on to the rails where the fenders sit. I was not able to get the name of it. Does anybody have a clue what this is. And could we use it on the A Bodies? Thanks.
Ned Payne
1966 Barracuda