Mower blades are the most important component of the machine next to the engine and are responsible for how attractive your lawn looks after the job is completed. Dull blades, or blades that are rotating erratically, can cause the lawn to look uneven and can damage the mower in certain cases. Adjusting the mower blades height will also determine how healthy your grass is, as different grasses require different heights to thrive in hot and cold weather.
Drain the mower of gas and oil, and disconnect the spark plug from the engine to prevent leaks and to keep the mower starting while you are working on it.
Turn the mower on its side so that the gas tank is underneath the carburetor to prevent gas from leaking into it. Even a few drops of gas can cause the carburetor to fail.
Secure the blade of the mower against the wood block so that it does not move, and tighten it accordingly so that it no longer wobbles. Use the penetrating oil on the bolt, and remove the bolt using the wrench if the blade is severely damaged and requires replacement.
Install the new blade, and tighten it using the wrench so that it does not wobble. Fill the mower with gas and oil, and test the new blade.
Use the height adjuster on the side of the mower to adjust the height of the deck over the grass. On most push mowers this is on the front of the mower as a small lever you can move forward and backward. Check the height using a tape measure to ensure it is adjusted properly.