You can line them up any way you want when you put them on. Some spin at different rates, others don't depending on your mower. They can't hit each other unless something breaks, and the lift you get from them is enough that the airflow around the blade tips doesn't affect the grass under the next blade. Be more concerned that all your baffles under the deck are in good shape, but even that is minor unless you're a lawn perfectionist. If you are, you probably want a reel type mower anyways. /forums/images/graemlins/smile.gif