An apparatus for providing a reference indication to a patient tissue, the apparatus comprising: a primary locating block including a patient-specific primary mating surface contoured for mating contact with a portion of the patient tissue, the primary mating surface being custom-configured to mate with the patient tissue in a predetermined primary mating orientation responsive to preoperative imaging of the patient tissue, and at least a first and a second mounting features ; at least a first and a second secondary items configured for selective engagement with the primary locating block, the secondary items being at least one of a noncustomized stock secondary item and a patient-specific secondary items, the first secondary item providing a first reference indication to at least a portion of the patient tissue, the second secondary item providing a second reference indication to at least a portion of the patient tissue distinct from the first reference indication; wherein the first mounting feature of the primary locating block is configured for engagement with the first secondary item in a predetermined first secondary mounting relationship, the first secondary mounting relationship being custom-configured for the patient tissue responsive to preoperative imaging of the patient tissue; further wherein the second mounting feature of the primary locating block is configured for engagement with the second secondary item in a predetermined second secondary mounting relationship, the second secondary mounting relationship being custom-configured for the patient tissue responsive to preoperative imaging of the patient tissue. a primary locating block including a patient-specific primary mating surface contoured for mating contact with a portion of the patient tissue, the primary mating surface being custom-configured to mate with the patient tissue in a predetermined primary mating orientation responsive to preoperative imaging of the patient tissue, and at least a first and a second mounting features ; at least a first and a second secondary items configured for selective engagement with the primary locating block, the secondary items being at least one of a noncustomized stock secondary item and a patient-specific secondary items, the first secondary item providing a first reference indication to at least a portion of the patient tissue, the second secondary item providing a second reference indication to at least a portion of the patient tissue distinct from the first reference indication; wherein the first mounting feature of the primary locating block is configured for engagement with the first secondary item in a predetermined first secondary mounting relationship, the first secondary mounting relationship being custom-configured for the patient tissue responsive to preoperative imaging of the patient tissue; further wherein the second mounting feature of the primary locating block is configured for engagement with the second secondary item in a predetermined second secondary mounting relationship, the second secondary mounting relationship being custom-configured for the patient tissue responsive to preoperative imaging of the patient tissue. <EOS>