How do you install mower blade for craftsman 21in?

For a walk behind rotary lawn mower:

1. Remove spark plug wire (to prevent an accidental start)
2. Tip mower up at about a 45 degree angle (have the air filter up to prevent getting oil in it)
3. Using a wrench turn the blade bolt counter-clock wise to remove the blade (if the blade is difficult use a block of wood to wedge between the blade and the deck to prevent it from spinning
4. Reverse the procedure to reinstall