Caster on a unmarked LBracket front end

[Dale]

Can you use a protractor to find were the caster is set on a L Bracket front end? steel has a line but not the aluminum Ls

 

[Bumpy]

I don't see why not.
I don't think it will be super accurate.
Place the bottom edge of the protractor at the bottom edge of the L bracket and put a plumb/vertical straightedge up from that same point and it should read a degree
on the far end of the protractor.
Probably going to require 3 hands.