A guide for assisting with attachment of a stock prosthetic implant to a patient tissue, the guide comprising: a lower guide surface configured to contact an upper implant surface of the stock prosthetic implant when a lower implant surface of the stock prosthetic implant is in contact with the patient tissue, at least a portion of the lower guide surface being contoured to substantially mate with at least a portion of the upper implant surface; an upper guide surface spaced longitudinally apart from the lower guide surface by a guide body, the upper guide surface being accessible to a user when the lower guide surface is in contact with the upper implant surface; at least one guiding aperture extending through the guide body between the upper and lower guide surfaces (430, 528) at a predetermined aperture location with respect to the guide body, the at least one guiding aperture defining a predetermined target trajectory through the guide body, and the at least one guiding aperture being collinear with a corresponding at least one fastener aperture in the stock prosthetic implant when the lower guide surface is mated with the upper implant surface; and a predetermined number of guiding apertures, each guiding aperture of the guide being configured to be collinear with one of the corresponding fastener apertures when the lower guide surface is mated with the upper implant surface; characterized in that at least one of the target trajectory and the aperture location of each guiding aperture is preselected responsive to preoperative imaging of the patient tissue; the guide includes at least one locating protrusion extending from the lower guide surface toward the upper implant surface, the at least one locating protrusion being configured to nest into a preselected one of the fastener apertures; and the at least one locating protrusion is spaced apart from each of the guiding apertures. a lower guide surface configured to contact an upper implant surface of the stock prosthetic implant when a lower implant surface of the stock prosthetic implant is in contact with the patient tissue, at least a portion of the lower guide surface being contoured to substantially mate with at least a portion of the upper implant surface; an upper guide surface spaced longitudinally apart from the lower guide surface by a guide body, the upper guide surface being accessible to a user when the lower guide surface is in contact with the upper implant surface; at least one guiding aperture extending through the guide body between the upper and lower guide surfaces (430, 528) at a predetermined aperture location with respect to the guide body, the at least one guiding aperture defining a predetermined target trajectory through the guide body, and the at least one guiding aperture being collinear with a corresponding at least one fastener aperture in the stock prosthetic implant when the lower guide surface is mated with the upper implant surface; and a predetermined number of guiding apertures, each guiding aperture of the guide being configured to be collinear with one of the corresponding fastener apertures when the lower guide surface is mated with the upper implant surface; characterized in that at least one of the target trajectory and the aperture location of each guiding aperture is preselected responsive to preoperative imaging of the patient tissue; the guide includes at least one locating protrusion extending from the lower guide surface toward the upper implant surface, the at least one locating protrusion being configured to nest into a preselected one of the fastener apertures; and the at least one locating protrusion is spaced apart from each of the guiding apertures.