If the bits in the BIT CARTRIDGE need to be replaced, remove it by pushing it up from the window underneath. Make sure to pull the COVER all the way back. Replace the bits with the desired bits. Ensure the bits are properly positioned in the cartridge and are not protruding from the back of the BIT CARTRIDGE. Or simply pull a bit from the holder and replace it with the desired bit. It will load into the cartridge automatically when the cover is opened.