An end effector for a surgical fastening device, the end effector comprising: a body defining a longitudinal axis ("L"); at least one fastener having an unformed configuration and a formed configuration, the at least one fastener including first and second arms (144d, 144e), the first and second arms extending in opposite directions, the first arm having first and second elbow segments (144b, 144g), the first elbow segment configured to bend as the at least one fastener is formed, the second elbow segment configured to remain unbent as the at least one fastener is formed, wherein the at least one fastener further includes a backspan that extends between the first and second arms; an anvil pivotally coupled to the body and movable between a first position and a second position, the anvil configured to engage the at least one fastener while in the first position and to disengage from the at least one fastener while in the second position; a pusher configured to advance the at least one fastener distally through the body and into engagement with the anvil to form the at least one fastener against the anvil; wherein the fastener has more than three sides while the first and second arms are in the unformed configuration and only three sides while the first and second arms are in the formed configuration, wherein each of the first and second arms include a crossing segment and a tissue engaging segment, wherein as the first and second arms are moved from the unformed configuration to the formed configuration, the crossing segments of the first and second arms converge toward the backspan and the tissue engaging segments of the first and second arms converge toward one another. a body defining a longitudinal axis ("L"); at least one fastener having an unformed configuration and a formed configuration, the at least one fastener including first and second arms (144d, 144e), the first and second arms extending in opposite directions, the first arm having first and second elbow segments (144b, 144g), the first elbow segment configured to bend as the at least one fastener is formed, the second elbow segment configured to remain unbent as the at least one fastener is formed, wherein the at least one fastener further includes a backspan that extends between the first and second arms; an anvil pivotally coupled to the body and movable between a first position and a second position, the anvil configured to engage the at least one fastener while in the first position and to disengage from the at least one fastener while in the second position; a pusher configured to advance the at least one fastener distally through the body and into engagement with the anvil to form the at least one fastener against the anvil; wherein the fastener has more than three sides while the first and second arms are in the unformed configuration and only three sides while the first and second arms are in the formed configuration, wherein each of the first and second arms include a crossing segment and a tissue engaging segment, wherein as the first and second arms are moved from the unformed configuration to the formed configuration, the crossing segments of the first and second arms converge toward the backspan and the tissue engaging segments of the first and second arms converge toward one another.