Follow the step by step:
1. First, make sure you disconnect the saw from the power source by either unplugging the unit from the mains or removing the battery.
2. To remove a circular saw blade, raise the lower guard and wedge the blade into a piece of scrap wood material.
3. Place the wrench into the head of the blade bolt. Position the arm of the wrench at 9 o'clock.
4. With the handle of a screwdriver or hammer, strike the long arm of the wrench downward in a counter clockwise direction. When you hit the wrench, the motor and bolt will turn, but it is the jarring action on the bolt, which should loosen the bolt.
5. unthread the bolt with your fingers in a counter-clockwise direction.