How to verify the pitch #of nuts?

I'm confused, true position has nothing to do with thread pitch? 

But to confirm the pitch of a threaded feature you can do it many ways, with varying degrees of accuracy. 
I would recommend a thread plug gage.
A pitch gage set (cheap and easy)
Make a mold of the part and check it with an optical system and measure it... 

I would like to confirm the pitch and direction :

We could find out the nut or thread bolt type from the drawing, then we could find out pitch # from manufacture data or google the type to get them. But how to determine plus or minus ?

If the probe moving down the thread direction, we use plus ? What happen if the probe moves against the thread direction ( Should we avoid this kind of situation?) , should we use minus?

Thank you

I would like to confirm the pitch and direction :

We could find out the nut or thread bolt type from the drawing, then we could find out pitch # from manufacture data or google the type to get them. But how to determine plus or minus ?

If the probe moving down the thread direction, we use plus ? What happen if the probe moves against the thread direction ( Should we avoid this kind of situation?) , should we use minus?

Thank you