Wear appropriate safety equipment.  Follow manufacturer’s recommendations (such as remove spark plug wire) before trying to remove the mower blade.  Place the tool (1) over the blade(2) allowing the stopping edge (3) to be installed on the outside edge of the mower deck. The retaining bolt (4) MUST be installed at this point. Now the blade can be loosened by first rotating it until the tool is solidly against an obstruction on the mower deck such as a wheel mount. When the blade can no longer move, apply as much force as needed to loosen blade nut or bolt.  You can now change or sharpen the mower blade.

To re-install mower blade, simply turn blade (2) and this tool (1) in the opposite direction as it was in taking it off. Allow device to again rotate slowly and strike mower deck obstruction securely. Tighten blade retaining nut or bolt to the manufacturer’s specification.