(Image credit: Shutterstock) Gaining a perfect lawn isn’t just about regular mowing, weeding, aerating and plenty more besides; it’s about the finishing touches that give it the edge. While you spend time tackling dandelions and crabgrass , removing thatch and fertilizing your lawn, there’s one task that often gets forgotten. The secret to a beautiful lawn is neat edges, with a clean line defining the lawn and its borders. Defining the 3-inch lawn edging rule (Image credit: Getty Images) This method involves creating a clean, crisp vertical edge with a sharp drop that separates your grass from the soil in your borders. In simple terms, it involves making a narrow 3-inch trench between the two areas. The vertical cut is deep enough to prevent grass from creeping over into your borders, as the 3-inch cut should sever most grass roots. It also creates a small gap between the turf and the soil that casts a shadow, further defining the space.…