Devices and processes for use in computer aided or computer navigated surgery include one or more locator and locking mechanisms and mating parts, or, alternatively, one or more adjustable locking structures interposed between an indicium and an item to be used during surgery such as a body part, tool, implant, trial or other structure or component. After the indicia have been registered into the system and surgery begun, it is sometimes desirable to remove and reattach the indicia for better access to the surgical sight, to avoid contamination of the indicia, or to accommodate other surgical needs. Locator and locking mechanisms and mating parts according to various embodiments are designed to be easily removable and accurately reattached so that the indicia can be repositioned relative to the item without the need to reregister the indicia into the system relative to the item. The locator and locking mechanism and mating parts preferably include structure that allows the indicia to be repositioned relative to the item in only one position and orientation, the position and orientation in which it was registered into the system originally. At other times during the surgery, it is desirable to selectively reposition the indicia to conform to anatomical constraints, for better array visibility, or to accommodate other surgical needs. In this situation, the adjustable locking structure allows quick and secure repositioning of the indicia with respect to the underlying item so that the constraints may be accommodated and the surgery may proceed with the assistance of computer guidance. The adjustable locking structure preferably includes structure to allow selective repositioning when desired but requires the adjustable locking structure to remain rigidly fixed when movement is not desired.