An apparatus comprising: an instrument body including: a plurality of protrusions configured to be sized according to an anatomy of a bone of a patient; and a guide (150, 170) configured to guide an aspect of a resection procedure of the bone, wherein the protrusion, when sized, is configured to abut the patient's bone to maintain the instrument body in a first position with respect to the bone during at least the aspect of the resection procedure; wherein the protrusions are sized to provide point contact with the bone to maintain the instrument body in the first position; wherein the guide is configured to guide pin placement within the bone; and wherein the guide includes a hole including a longitudinal axis, wherein, with the instrument body in the first position, the longitudinal axis aligns with an axis of a guide pin; wherein each protrusion extends outwardly from an interior surface of the instrument body; wherein the instrument body includes a condylar portion (112, 114) including a condylar protrusion (130A, 130B) extending from the condylar portion (112, 114) and configured to be sized according to the anatomy of the bone to abut a condyle of the femur of the patient; wherein each protrusion includes an initial length and is configured to be sized to a final length according to the anatomy of the bone, the protrusions, in the respective final lengths, being configured to abut the patient's bone to provide point contact with the bone and maintain the instrument body in the first position with respect to the bone during at least part of the resection procedure; and wherein the instrument body includes a patellar track portion; characterised in that the patellar track portion includes a patellar track protrusion extending from the patellar track portion and configured to be sized according to the anatomy of the bone to abut a patellar track of the femur of the patient. an instrument body including: a plurality of protrusions configured to be sized according to an anatomy of a bone of a patient; and a guide (150, 170) configured to guide an aspect of a resection procedure of the bone, wherein the protrusion, when sized, is configured to abut the patient's bone to maintain the instrument body in a first position with respect to the bone during at least the aspect of the resection procedure; a plurality of protrusions configured to be sized according to an anatomy of a bone of a patient; and a guide (150, 170) configured to guide an aspect of a resection procedure of the bone, wherein the protrusion, when sized, is configured to abut the patient's bone to maintain the instrument body in a first position with respect to the bone during at least the aspect of the resection procedure; wherein the protrusions are sized to provide point contact with the bone to maintain the instrument body in the first position; wherein the guide is configured to guide pin placement within the bone; and wherein the guide includes a hole including a longitudinal axis, wherein, with the instrument body in the first position, the longitudinal axis aligns with an axis of a guide pin; wherein each protrusion extends outwardly from an interior surface of the instrument body; wherein the instrument body includes a condylar portion (112, 114) including a condylar protrusion (130A, 130B) extending from the condylar portion (112, 114) and configured to be sized according to the anatomy of the bone to abut a condyle of the femur of the patient; wherein each protrusion extends outwardly from an interior surface of the instrument body; wherein the instrument body includes a condylar portion (112, 114) including a condylar protrusion (130A, 130B) extending from the condylar portion (112, 114) and configured to be sized according to the anatomy of the bone to abut a condyle of the femur of the patient; wherein each protrusion includes an initial length and is configured to be sized to a final length according to the anatomy of the bone, the protrusions, in the respective final lengths, being configured to abut the patient's bone to provide point contact with the bone and maintain the instrument body in the first position with respect to the bone during at least part of the resection procedure; and wherein the instrument body includes a patellar track portion; characterised in that the patellar track portion includes a patellar track protrusion extending from the patellar track portion and configured to be sized according to the anatomy of the bone to abut a patellar track of the femur of the patient.