Rectangular baler comprising a bale chamber (101, 201, 301), a compacting plunger (103, 203, 303) and a guide system comprising at least one guide assembly (131, 132； 2 3 1； 33 1, 332), comprising a guide element (133, 233, 333), and a threaded shaft (134, 234, 334) and nut (135, 235, 335) for positioning the guide element, wherein, for receiving said threaded shaft, an elongated slot (140, 240, 340) is provided extending in a slot direction making an angle (a) between 1 and 85 degrees with respect to the discharge direction (P), said threaded shaft being arranged in an upright position perpendicular to the slot direction.
