Dr. Feickert Protractor

Proper analog set up is something you want to get right. In my experience even the slightest variation from the standard that this tool allows you to hone in on, has a negative effect on sound quality. The Dr's tool just allows you to get "perfection" easier than any of the others I've used. It is expensive though.

The current edition offers 3 different scales to choose from. Lofgren, Baerwald and Stevenson the latter is really good for Rega tables. The beauty of the tool is it's ability to triangulate the three points of spindle, arm pivot and stylus overhang. I have used mine to set a Kleos on my RP10 and have found it very beneficial in set up. I used to use the MO-Fi disc and then bought the Avid plate. But the protractor provides a more precise method of measuring arm pivot to stylus. 
Also besides these features, the grid aids in getting the cartridge aligned at the proper angle. In truth it is a tool that I may only use once or twice again in life, but wouldn't want to set up a cartridge without it. 
That said the Avid plate actually had me very close and if you don't want to invest 250.00 the 45.00 for the Avid does a nice job as well. 

I wish there was a place to rent one for my setup.
I may only use it a couple times in my lifetime.

Dear @rdk777: All depends on the tonearm jig that comes with and how accurately it's.

The name of the game in cartridge/TT/tonearm set up is accuracy and you can buy for a lot less money than Dr's a dedicated protractor specific for your tonearm and that's the MINTLP and I think that you pay around 125.00.
The Dr's protractor that gives alignment type options means almost nothing. You only need one accurate alignment where Stevenson is out of question.

Regards and enjoy the MUSIC NOT DISTORTIONS,
R.