I am using the Boone and crocket web site and cant figure out the Greatest Spread Measurment. This is what the site reads

The greatest spread is measured between perpendiculars at a right angle to the center line of the skull at the widest part, whether across main beams or points

Thanks in advace

so if you split the skull in half.(dont actually split it in half haha) from nose to back of head, you measure at the widest point perpendicular from the line between the nose and back of skull.... if that makes sense...

Greatest spread is not used in the calcuation of inches, I do not know why they even need it.
Inside spread is the spread measurement that is calcualated for your score.