The replacement of the atlatl and dart weapon system with the bow and arrow system in the Basin-Plateau region was a significant technological event. Distinguishing dart points from arrow points is one component of understanding the timing of this event. Previous analyses demonstrated that size differences of shoulder widths distinguish dart from arrow points. However, neck width and thickness of a stone projectile point are better variables for differentiating arrow points from dart points because these variables directly relate to the attachment of a projectile point to a foreshaft or mainshaft. Because of overlaps in foreshaft diameters, projectile point neck widths, and thicknesses between darts and arrows, it is not always possible to separate projectile points into arrow points and dart points. In such cases, it is only possible to provide a probability estimate of correct classification for any individual specimen falling within the overlapping ranges.