The present invention provides a positioning device (16), having a front end (16f) and a rear end (16r) and having a longitudinal axis (LP), comprising a base plate (18) with at least one pair of first and second raised portions (30, 32) of respective lengths (LI, L2) and upstanding from the base plate (18) and one or more valley regions located between the raised portions (30, 32), wherein one of said raised portions (30 or 32) extends rearwardly of the other of said raised portions (32, 30) in the direction of axis LP by an amount (N). Such a device may be installed on an angled or rotary milking platform such as to ensure an even gap G between the positioner (16) and the rear (22) of the platform.
