This document discusses, among other things, a fiducial marker kit. In one example, the kit includes a fiducial marker assembly that includes a bone screw base for receiving an imageable marker or locatable divot. A valved protective sleeve prevents debris from accumulating in a receptacle portion of the base, which may otherwise degrade the accuracy of patient registration in an image-guided surgical procedure. In one example, the valve automatically opens or closes upon insertion or removal of a screwdriver or other tool, or a shaft portion of the imageable marker or locatable divot. Various bone screw base and receptacle combinations are also discussed.