"The switch only justs fits inside a metal box, there is no tolerance. If the box is only slightly distorted then there is no chance of getting the switch to fit. The only way is to let in the box by 5 mm and do not plaster up to the edge of the box or if you have then scrape the plaster back. Obviously you cannot do this if metal box is already installed flush to the edge. And the screws are rubbish, they stripped very easily. The brass terminals are quite narrow so that there is not much thread for the screws. In fact if the terminal is full of wire then it is impossible to get the screw in as the dome on the end of the screw is deeper than the depth of screw thread on the terminal. If you have hours to spare and are very patient then I guess they might be OK. Strictly for the DIYer. (who should not be doing it as it is in a kitchen and therefore covered by Part P)"