This invention relates to a shutter for use in physical vapour deposition apparatus having a chamber. The shutter, generally indicated at 5, is located in a side housing 6 of the vacuum chamber 7, whilst sputtering is taking place. Once the substrate 2 is treated, the substrate is removed from the chamber and the shutter is brought in to an operative position above a wafer pedestal or support 1. The shutter is mounted on an arm 8 using a fixing boss 10, the arm and the boss being magnetically coupled.