Abstract: The present invention provides an armboard attachment for supporting a humerus of a patient placed on a surgical table. The armboard attachment comprises a humerus support board for horizontally and laterally positioning the humerus of a patient on an upper surface thereof. The humerus support board has a central cut-out at the outboard edge that is sized to receive the lower arm of a patient when the upper arm is supported on the board. The armboard attachment includes a pair of bars extending downward from the support board that are configured to be clamped to an accessory rail of a surgical table. The attachment also includes a reinforcing bar extending along each side of the support board to prevent bending or buckling of the armboard attachment when in use.