Abstract: In a baler having a plunger reciprocating in a bale case and knotters for tying strands of twine around bales, two trip mechanisms are provided for automatic actuation of the knotters. A first trip mechanism is capable of preventing operation of the knotters until a bale of desired length is formed. A clutch mechanism for driving the knotters includes a pawl assembly with an abutment tab. A second trip mechanism holds the pawl assembly in a position where it prevents the knotters from being driven when the plunger is retracted. The initial displacement of the second trip mechanism toward a position where the knotters are driven is in substantially the same direction as the initial displacement of the pawl assembly abutment tab.