A loading unit for a surgical stapling apparatus includes a shaft assembly, anendeffector coupled to the shaft assembly, an I-beam assembly supported in theshaft assembly,and a fire lock assembly supported on the shaft assembly. The end effector ispositioned toarticulate relative to the shaft assembly between an unarticulated positionand an articulatedposition. The I-beam assembly is selectively movable relative to the endeffector to fire theend effector. The fire lock assembly is configured to prevent the I-beamassembly from firingthe end effector when the end effector is disposed in the unarticulatedposition.
