A roller guide (1) for guiding stock in a longitudinal feeding direction (A) toward a pair of rolls for shaping the stock. The roller guide comprises a frame arrangement (2), a pair of guide rollers (3, 4) configured to, in a closed position, engage opposite surface portions of the stock,and positioning means for adjusting a lateral distance between the guide rollers. The roller guide further comprises detection means (13) configured to detect a longitudinal position of a piece of stock (20) with respect to the guide rollers. The positioning means is configured to adjust the lateral distance between the guide rollers in response to said detection.