When it comes to unscrewing a lawn mower blade, there are two main things you should consider: the size of the bolt and its orientation. The size of the bolt will determine which type of tool you need in order to loosen it. A socket wrench or adjustable wrench is usually sufficient for most bolts, but if your model has larger bolts, then you may need an impact driver or even a breaker bar. Additionally, before attempting to loosen any bolts on your lawn mower blade, make sure that you orient yourself with the direction of unscrewing as many blades are reverse-threaded meaning they screw in clockwise and out counterclockwise - this is important to ensure that you don't strip or damage any threads when removing them.