A posterior-referencing apparatus for sizing the resected distal femur prior to implanting the femoral component of a total knee prosthesis. The apparatus can be used for sizing either the left or right femur. The apparatus has a first operable orientation adapted for sizing the left femur and a second operable orientation offset 180 degrees from the first operable position for sizing the right femur. The apparatus can be reconfigured between left and right orientations quickly and easily without disassembling the apparatus
