Disable the mower by disconnecting the spark plug from the engine. Pull the spark plug cover off of the spark plug. Place the appropriate sized spark plug socket over the spark plug and twist to remove.
Remove the gasoline from the mower with a gas siphon and place in a clean jar with a lid.
Tilt the mower to one side and prop it securely with bricks or wood. Remove the dead grass accumulated around the blade and bolt. Turn the blade and make a mental note of the direction the blade turns.
Place a wood wedge under the blade to keep it from moving.
Use the appropriate size wrench and fit it over the bolt holding the blade to the mower. To remove the bolt, turn the bolt in the same direction the blade spins.