There's a gap between my garage and the house behind's fence. This means their little angels keep wandering into my garden, despite being told by me and their mum not to. The gap is about 1 and 1/2 feet wide. On the one side is a brick wall (my garage) and the other a timber fence (my fence). It's at the back of my garage, so whilst I don't want it to be unduly ugly, I'll never have to see it. What can I put up that's cheap and easy, and keep uninvited visitors out? I've checked with the land registry, it's not a boundary I'm responsible for, so will erect it on my land. That way, if the lady behind prefer to continue her fence to my garage wall in her own time, she's free to do so.