This document discusses, among other things, fiducial marker devices, tools, and methods. One example illustrates a combined imagable fiducial locator and divot for receiving a positioning wand of an image-guided surgical (IGS) workstation. A further example is reflective such that it is locatable by a remote detector of an optical positioning system. A generally cylindrical (e.g., faceted cylindrical) columnar locator permits easy application of reflective tape. Other examples discusses a unitary fiducial marker with multiple divots and a swiveling and/or tilted fiducial marker divot, each of which allows manipulation of a positioning wand into a remote camera's field of view. Another example includes at least one reflector that can be aimed. A further example discusses an imagable fiducial marker carrier that is attachable to a single location on a patient's skull to reduce trauma. A keying arrangement fixedly defines the orientation of the carrier, allowing detachment and reattachment in the same orientation.