Engage the parking brake and disconnect the battery to ensure the mower's motor doesn't somehow accidentally engage.
Place a cloth around the blade to protect yourself from accidental injury.
Use a 1/2-inch hexagonal socket wrench to unscrew the bolt anchoring the blade. Carefully remove the old blade.
Position the new blade with the curled part of the blade facing upward and the sharper cutting edge facing downward.
Align the star with the mandril. The mandril is a small, multi-sided metallic object under the mower deck that attaches to the blade.
Use the socket wrench to tighten the bolt.
Reconnect the battery.