Lawnmowers cut grass with the aid of a rapidly spinning blade. Depending on what kind of lawnmower you have, you may have one single lawnmower blade on your lawnmower, or it may have multiple blades. Over time the blade will become dull and need to be sharpened or replaced. The blade can become compromised faster if it hits a bunch of stones or sticks. When it comes time to sharpen or replace the blade, you'll have to remove it from the lawnmower. It is not difficult to loosen a lawnmower blade so that you can remove it.
Disable the lawnmower by detaching the spark plug cord. You may want to completely remove the spark plug with a spark plug wrench to ensure the lawnmower can't start up.
Remove the gasoline out of the lawnmower. This can be accomplished by either running the lawnmower until it runs out of gas or by siphoning it out.
Turn the lawnmower on its side and prevent the blade from turning by wedging a two by four in between the blade and mower deck. Remove the bolt that holds on the lawnmower blade. A simple box wrench or adjustable wrench will be sufficient to remove the bolt.
Remove the lawnmower blade from the mower deck. Now it can be sharpened or replaced.