A synthetic resin frame, having a single foot extending laterally from it, has a roller mounted for rotation about a bearing element that extends into holes in the sides of the frame. A combination line guard and bearing-retaining element is snapped over the frame. The ends of the line guard and bearing-retaining element hold the bearing in position, while openings in the line guard guide the line and substantially prevent it from contacting the synthetic resin. The line guard and bearing retainer is formed of material more wear resistant than that of the frame.