It's always preferable to nail through the thinner piece into the thicker piece. Driving the nail at an angle may not be attractive, but will give you a stronger hold. Use a nail that is long enough to allow approximately two thirds of the nail to be driven into the thicker piece.
When water flows backward through the water supply system, it is called backsiphonage or backflow. When that water is accidentally mixed with hazardous chemicals or bacteria, it is called dangerous! For this reason, never use spray attachments without a backflow prevention device. The chemicals used on your lawn are toxic and can be fatal if ingested.