This method determines the coefficient of static friction of most packaging materials by measuring the angle at which one test surface begins to slide against another inclined surface as the incline is increased at a constant and prescribed rate. The test is frequently referred to as slide angle. The coefficient of friction is numerically equivalent to the tangent of that angle.
ANSI/TAPPI T815 om-2012 history
2012ANSI/TAPPI T815 om-2012 Coefficient of static friction (slide angle) of packaging and packaging materials (including shipping sack papers, corrugated and solid fiberboard) (inclined plane method)