An employee climbed up to the penthouse (a small area three levels up) to manually adjust the 4-way diverter to be over the correct bin prior to starting the next order. The employee opened one of the access doors on the 4-way diverter to visually observe the bin to which the diverter was directed. The employee went to brush debris from the manual diverter near the airlock and made contact with the airlock which had not been locked out. The employee sustained an amputation to the right ring fingertip.