Abstract: A marking apparatus that is useful for marking a line upon a ridge protruding from a surface of a continuously passing elongated article is disclosed. A stylus member of the marking apparatus has a notch in its foot, through which the ridge on the article passes. A tracking arm member is pivotally attached to a bar member, and supports the stylus member, so that the stylus member can follow the track of the ridge even if the article wanders from side to side as it passes the marking apparatus. Marking fluid, stored in a reservoir, passes through a hollow tube and a bore through the stylus member which communicates with the notch in the foot of the stylus member.