Abstract: An apparatus for squaring or trimming the edges of the elastomeric (uncured) cover of an industrial belt. An edge sensor is disposed to track each of the edges of a bare or uncovered carcass foward of the calender nip in which the cover is applied. Rotating trim blades for trimming excess gum from the respective edges of the covered belt are moved laterally proportionally to the algebraic sum of the deviations of the edges of the carcass from their respective ideal lines. Thus, an adequate but not excessive amount of the cover gum is provided to cover the respective edges of the carcass of the belt. The respective edge sensors are hydraulically connected with the trim blades for synchronized movement so as to maintain the described thickness of cover gum outwardly from the edges of the carcass.