We have moved into a new home. The front border has a picket fence. There is a distance of about 3 metres between the footpath and the fence. In our front yard we have couch lawn, which is also between the footpath and the fence. I want to get rid of all the grass in our front yard and go native and woodchip. How do I stop the grass from the verge growing under the fence? What sort of barrier will work best and where would I buy it?