Abstract: An automatic threading apparatus for a magnetic tape transport is disclosed in which a flexible sprocketed guide tape loop is disposed in a continuous guide channel which is shaped to conform to the shape of the complex tape path extending from the supply reel to the take-up reel of the magnetic tape transport. The guide tape is driven by a sprocketed gear to move in sliding engagement with the continuous channel in either direction to move a leader block coupling device attached to the sprocket tape from a first position adjacent the supply reel where the leader block is coupled and decoupled from the device to a second position associated with the take-up reel where the leader block is maintained coupled to the device and caused to rotate relative thereto by and with the take-up reel during a winding operation.