You know what really gets me?
With 360 degrees to choose from, you are working from a pattern, and they are offering you a template.
I can see the block ... it is a spike and peaky, and should be something I can easily measure, but darn! Their template is one or two degrees different than any measurement known to man/woman (as the case may be) .... or <g> they have a "special" ruler you can buy for just a "little more" money ....
I really should have paid more attention in trig class .... but, no one had a clue that this old farm girl would ever come in THIS direction! LOL ...
Thank you for explaining the basics to it so that I can understand.