When you are putting up that new picture where do you hang it??
Not everyone realises that cables, (if correctly installed) run in very specific areas in the wall. Cables should NOT run diagonally, so if you have a switch or a socket cables should run either horizontally to/from it or vertically to/from it. Its a good idea to think of this BEFORE you put that picture hook in the wall!
We were called out this week because a house had lost some of its power just 6 weeks after we had just installed a new consumer unit , the RCD had tripped. The fault was traced to an old picture hook where the nail had gone through a cable, presumably it had been close to going through the insulation before, someone knocked it and that was enough for the nail to touch the copper. Good job the board had been changed otherwise the fault would not have been detected! So remember check before you hammer in the nail!