 Likewise, the pinch roller in a magnetic tape transport is a type of idler wheel, which presses against the driven capstan to increase friction.In a belt drive system, idlers are often used to alter the path of the belt, where a direct path would be impractical.Idler pulleys are also often used to press against the "back" of a pulley in order to increase the wrap angle (and thus contact area) of a belt against the working pulleys, increasing the force-transfer capacity.