A tractor for feeding perforated webs, such as perforated paper, to present successive lines for printing in a computer printer, typewriter or the like has a frame which locates a sprocket and a belt having pins projecting from the pitch line of the belt and lugs which are driven by the sprocket. In order to provide precision feeding of the web and to minimize drag and jamming, the lid is arranged with respect to the frame so that the web is maintained at or substantially at the pitch line of the belt in the region where the pins enter the perforations, are engaged by the perforations and leave the perforations. The distance between the surface of the lid which faces the belt and the belt surface is limited such that the perforations contact the pin surface below a critical position where the web clings to the pins. This is the position of repose where the angle between the surface of the belt and a line from the position of repose perpendicular to a tangent to the pin surface at that position which intersects the belt surface is equal to the arc tangent of the coefficient of friction between the web and pin materials. The lid surface is preferably provided by a rib extending the length of the lid so as to overlie and extend beyond the aforesaid region of entry and engagement of the pins and web perforations. This rib has a wall which provides a thrust surface against which the pins in the region can bear to accommodate the side thrust toward the center of the web when the web is driven by two tractors engaging rows of perforations along the opposite edges of the web.