Motor would not turn on

Initially removed carbon brushes then inserted the new carbon brushes. The motor still did not turn on. Then I removed the brushes again, used a flashlight to look in the hole where the carbon brushes are installed. I noticed that there was a square notch on one side of the hole. I then reinstalled the carbon brushes, ensuring that the beveled side of the carbon brush was installed so it lines up with the square notch. This allows the carbon brushes to touch the motor. I turned the unit on and it worked.