An orthopaedic surgical instrument comprising a metallic customized patient-specific surgical instrument is disclosed. The metallic customized patient-specific surgical instrument includes a base plate sized to be positioned on a resected surface of a distal end of a patient's femur, an anterior resection guide body attached to, and extending from, the distal surface of the base plate to a free distal end, a posterior resection guide body attached to, and extending from, the distal surface to a free distal end, and a pair of chamfer resection guide bodies attached to, and extending from, the distal surface.