Bogen / Manfrotto 3157N Rectangular Quick Release Plate (RC2 System) with 1/4-20" Scr

I wanted to get a quick release plate for my 488rc2 ball head.

It has a screw through one of the holes that I don't think I need but I couldn't get it to screw out. Can anyone affirm that this is the right QRP for this ballhead?

It is listed under accessories for that head on B&H's site.
Is there a purpose for the screw?

Thanks,

Nic

I had a bunch of RC2 accessories before I upgraded to the RC4 system and Im trying to think of what screw you are talking about...? Is it on the plate itself or the ballhead?

Now that I put my reading glasses on, it looks like a set screw except the threads have a cover over them and it's just a smooth stud about the same length as the camera screw.

Here's a picture on B&H: http://www.bhphotovide​o.com …_Quick_Release_​Plate.html

I'm reading on another site - maybe it's an "anti-twist pin?"

I found another thread my searching on "anti-twist pin"

Oh I see what youre talking about! That little black thing next to the mount screw. Huh, I really dont remember ever having that there and certainly dont recall needing or using it. I think you might be right though in thinking that its for some alignment or anti-twist thing.

I grabbed it with a small pair of pliers and yanked it and it came right out.