A guide and a stock instrument in combination. The stock instrument includes a guide interacting feature, a lower instrument surface to abut the patient tissue and an upper instrument surface for contacting the guide. The guide includes a guide body including a lower guide surface and an upper guide surface. The lower guide surface mates with the upper instrument surface of the stock instrument when the lower instrument surface is in contact with the patient tissue. The lower guide surface includes an instrument guiding feature to mate with the guide interacting feature. An orienting feature including an arm extends away from the upper guide surface. The arm has a landmark engaging portion to enter a predetermined relationship with a fixed landmark on the patient tissue. The predetermined relationship indicates that the stock instrument has achieved a predetermined instrument relationship with the patient tissue.
