Unlike ordinary snap traps for the homeowner, these traps are specifically designed for professional pest management use. Both mouse and rat traps should be set on a hard surface perpendicular to a wall so that the trigger end is toward the wall. This trap is also the choice of professionals for trapping voles. Place the trap perpendicular(across) the trail in the grass, you may need to trim the grass in the spot where the trap sits. The voles will run across the expanded yellow plastic triggering plate and be captured.