An instrument for shaping a medullary canal of both a patient's left leg and right leg, comprising: (a) a handle that includes a handle longitudinal axis; (b) a shaping member including: structure configured to shape bone; a shaping member longitudinal axis, and a connecting structure that includes an interpositional cooperation structure (72,74); (c) an offset member that physically connects the handle to the shaping member, the offset member extending in an offset direction that includes a first directional component in a first direction orthogonal to the longitudinal axis of the shaping member, and a second directional component in the direction of the shaping member longitudinal axis; (d) the offset member including: (i) a first opening adapted to receive the shaping member connecting structure, the first opening configured to receive the shaping member connecting structure in a manner whereby the shaping member longitudinal axis is substantially parallel to the handle longitudinal axis; (ii) a second opening adapted to receive the shaping member connecting structure, the second opening configured to receive the shaping member connecting structure in a manner whereby the shaping member longitudinal axis is substantially parallel to the handle longitudinal axis; and (e) a retention device or member comprising an actuator and at least one interpositional structure, the retention device or member configured to interpose the at least one interpositional structure relative to the interpositional cooperation structure of the shaping member connecting structure when the actuator is actuated. (a) a handle that includes a handle longitudinal axis; (b) a shaping member including: structure configured to shape bone; a shaping member longitudinal axis, and a connecting structure that includes an interpositional cooperation structure (72,74); structure configured to shape bone; a shaping member longitudinal axis, and a connecting structure that includes an interpositional cooperation structure (72,74); (c) an offset member that physically connects the handle to the shaping member, the offset member extending in an offset direction that includes a first directional component in a first direction orthogonal to the longitudinal axis of the shaping member, and a second directional component in the direction of the shaping member longitudinal axis; (d) the offset member including: (i) a first opening adapted to receive the shaping member connecting structure, the first opening configured to receive the shaping member connecting structure in a manner whereby the shaping member longitudinal axis is substantially parallel to the handle longitudinal axis; (ii) a second opening adapted to receive the shaping member connecting structure, the second opening configured to receive the shaping member connecting structure in a manner whereby the shaping member longitudinal axis is substantially parallel to the handle longitudinal axis; and (i) a first opening adapted to receive the shaping member connecting structure, the first opening configured to receive the shaping member connecting structure in a manner whereby the shaping member longitudinal axis is substantially parallel to the handle longitudinal axis; (ii) a second opening adapted to receive the shaping member connecting structure, the second opening configured to receive the shaping member connecting structure in a manner whereby the shaping member longitudinal axis is substantially parallel to the handle longitudinal axis; and (e) a retention device or member comprising an actuator and at least one interpositional structure, the retention device or member configured to interpose the at least one interpositional structure relative to the interpositional cooperation structure of the shaping member connecting structure when the actuator is actuated.