A system for creating a virtual bite line in connection with an article of footwear, the system comprising: marking mechanism that applies conditionally visible indicia to a surface of a shoe upper at an interface of the shoe upper and a bottom unit when the shoe upper and the bottom unit are temporarily joined with a predetermined amount of force, wherein the conditionally visible indicia are detectable only under predetermined lighting conditions; a first light source that projects light across at least a portion of the marked shoe upper, the projected light intersecting the conditionally visible indicia at at least one point to create an intersection; and at least one camera that detects the intersection between the projected light and the conditionally visible indicia.