Type of the ratchet mechanisms Externally meshed Internally meshed Ratchet rack Tooth ratchet mechanisms Fixed direction Single function Changeable direction 1, 2 Double function External Silent ratchet mechanisms InternalType of the ratchet mechanisms Silent ratchet mechanisms Externally meshed Internally meshed Ratchet rack Fixed direction Changeable direction1,2 Single function Double function External Internal Tooth ratchet mechanisms