An end effector, comprising: a mounting portion; a first jaw member extending distally from the mounting portion, the first jaw member including a tissue engaging surface; a second jaw member extending distally from the mounting portion and supporting a drive beam, the second jaw member being pivotable relative to the first jaw member between an unapproximated state and an approximated state; and a fastener cartridge secured to the second jaw member and supporting a plurality of fasteners in fastener retaining slots defined in a tissue engaging surface of the fastener cartridge, the drive beam being configured to distally translate along the first jaw member and the second jaw member to approximate the first and second jaw members relative to one another, and distally translate along the fastener cartridge to fire the plurality of fasteners from the fastener retaining slots and form the plurality of fasteners against the tissue engaging surface of the first jaw member, characterized in that said end effector further comprises: a lever assembly including a lever pivotally connected to the first jaw member and pivotally movable relative to the first jaw member between an extended position and a retracted position; and a notch defined in the drive beam, the lever being engaged with the notch when the first and second jaw members (410,420) are in the unapproximated state, when the drive beam is in a proximal position, and when the lever is in the extended position, the lever being thus engaged with the notch of the drive beam to limit distal translation of the drive beam prior to the second jaw member pivoting relative to the first jaw member from the unapproximated state to the approximated state thereby to facilitate said pivoting of the second jaw member. a mounting portion; a first jaw member extending distally from the mounting portion, the first jaw member including a tissue engaging surface; a second jaw member extending distally from the mounting portion and supporting a drive beam, the second jaw member being pivotable relative to the first jaw member between an unapproximated state and an approximated state; and a fastener cartridge secured to the second jaw member and supporting a plurality of fasteners in fastener retaining slots defined in a tissue engaging surface of the fastener cartridge, the drive beam being configured to distally translate along the first jaw member and the second jaw member to approximate the first and second jaw members relative to one another, and distally translate along the fastener cartridge to fire the plurality of fasteners from the fastener retaining slots and form the plurality of fasteners against the tissue engaging surface of the first jaw member, characterized in that said end effector further comprises: a lever assembly including a lever pivotally connected to the first jaw member and pivotally movable relative to the first jaw member between an extended position and a retracted position; and a notch defined in the drive beam, the lever being engaged with the notch when the first and second jaw members (410,420) are in the unapproximated state, when the drive beam is in a proximal position, and when the lever is in the extended position, the lever being thus engaged with the notch of the drive beam to limit distal translation of the drive beam prior to the second jaw member pivoting relative to the first jaw member from the unapproximated state to the approximated state thereby to facilitate said pivoting of the second jaw member. a lever assembly including a lever pivotally connected to the first jaw member and pivotally movable relative to the first jaw member between an extended position and a retracted position; and a notch defined in the drive beam, the lever being engaged with the notch when the first and second jaw members (410,420) are in the unapproximated state, when the drive beam is in a proximal position, and when the lever is in the extended position, the lever being thus engaged with the notch of the drive beam to limit distal translation of the drive beam prior to the second jaw member pivoting relative to the first jaw member from the unapproximated state to the approximated state thereby to facilitate said pivoting of the second jaw member.