a surgical severing and stapling instrument , suitable for laparoscopic and endoscopic clinical procedures , clamps tissue within an end effector of an elongate channel pivotally opposed by an anvil . an e - beam firing bar moves distally through the clamped end effector to sever tissue and to drive staples on each side of the cut . the e - beam firing bar affirmatively spaces the anvil from the elongate channel to assure properly formed closed staples , especially when an amount of tissue is clamped that is inadequate to space the end effector . in particular , an upper pin of the firing bar longitudinally moves through an anvil slot and a channel slot is captured between a lower cap and a middle pin of the firing bar to assure a minimum spacing . forming the e - beam from a thickened distal portion and a thinned proximal strip enhances manufacturability and facilitates use in such articulating surgical instruments .