A handle assembly for a surgical stapler comprising an elongate shaft having a proximal end and a distal end, the elongate shaft defining a longitudinal axis between the proximal end and the distal end, and a jaw assembly disposed at the distal end of the elongate shaft, the handle assembly comprising: a housing; an actuation mechanism positioned within the housing and comprising: an advancing driver; a reversing driver; and an actuation shaft extending along the longitudinal axis, the actuation shaft rotatably coupled to the housing with respect to the longitudinal axis, and the actuation shaft comprising: an advancing rack extending longitudinally along the actuation shaft; and a reversing rack extending longitudinally along the actuation shaft, the reversing rack offset from the advancing rack with respect to an angular position on the actuation shaft relative to the longitudinal axis; and a coupler adapted to engage the elongate shaft of the surgical stapler, and characterized in that the actuation shaft is rotatable between a first orientation in which the advancing driver engages the advancing rack and a second orientation in which the reversing driver engages the reversing rack. a housing; an actuation mechanism positioned within the housing and comprising: an advancing driver; a reversing driver; and an actuation shaft extending along the longitudinal axis, the actuation shaft rotatably coupled to the housing with respect to the longitudinal axis, and the actuation shaft comprising: an advancing rack extending longitudinally along the actuation shaft; and a reversing rack extending longitudinally along the actuation shaft, the reversing rack offset from the advancing rack with respect to an angular position on the actuation shaft relative to the longitudinal axis; and a coupler adapted to engage the elongate shaft of the surgical stapler, and characterized in that the actuation shaft is rotatable between a first orientation in which the advancing driver engages the advancing rack and a second orientation in which the reversing driver engages the reversing rack. an advancing driver; a reversing driver; and an actuation shaft extending along the longitudinal axis, the actuation shaft rotatably coupled to the housing with respect to the longitudinal axis, and the actuation shaft comprising: an advancing rack extending longitudinally along the actuation shaft; and a reversing rack extending longitudinally along the actuation shaft, the reversing rack offset from the advancing rack with respect to an angular position on the actuation shaft relative to the longitudinal axis; and an advancing rack extending longitudinally along the actuation shaft; and a reversing rack extending longitudinally along the actuation shaft, the reversing rack offset from the advancing rack with respect to an angular position on the actuation shaft relative to the longitudinal axis; and a coupler adapted to engage the elongate shaft of the surgical stapler, and characterized in that the actuation shaft is rotatable between a first orientation in which the advancing driver engages the advancing rack and a second orientation in which the reversing driver engages the reversing rack.