Dear Mary: how to rumble a snooper

Q. I like and get on well with my sister-in-law. My problem is that she is incredibly nosy and I always feel she is itching for a chance to go through my private papers. I can hardly lock the room where they are kept, so it means I have to keep an eye on her – almost as much as you would a toddler – all the time she is in our house. What do you suggest, Mary?

– Name and address withheld

A. Source an A4-sized documents box – the sort that you close with a ribbon. Lay the box on its back and fill with marbles. Tie the ribbon to shut the contents in and place the box, ribbon-side down, in a bookshelf with its back superglued to the wall. Put a sticky label on the front saying: ‘Super private papers – confidential.’ Then go shopping. Your sister-in-law will be tempted to take the box down so she can peep inside, but as she attempts to do so she will undo the ribbons.