This is the only thing I have found that I can make that will actually sell. It can't be patented, the idea was covered by a patent that expired a long time ago. I have made well over a hundred of these, they used to cost 25p each to make and sell very well on Ebay for £1. They don't tend to sell well above £1. THIS IS NOT TO PROTECT CHILDREN. THIS IS TO PROTECT EQUIPMENT FROM CHILDREN. The design looks strange, but that is because I searched for information on every mains socket I could find then used the data gained to make this design that should fit every available Mains Socket. This is version 4, previous versions were simpler in design, but could get returned due to not fitting. This design has never been returned.I have printed in various colours in ABS and PLA, it prints well in either. I usually print at 0.3mm layer but any layer size should work. It's a thin plate, so infill doesn't matter. After printing you need to remove the support from under the switch. This was not my idea, it was a request from my daughter. Around age of 6 months to a year and a half when young children become mobile, they tend to discover mains switches that make a really nice clicky sound. With UK mains sockets this is not really a safety issue to the child, but it can be a safety issue for equipment plugged into that socket. Switching off Sky boxes in mid record is annoying, multiple switching of PC causes it to fail expensively. This simple plate stops children from accessing the switch.