It is often desirable to define objects with respect to images of an anatomy displayed using an image guided surgery system. In a double-roller tripod type constant velocity universal joint, a track gap \u03b41 between one of the roller guiding surfaces formed on both sides of a track groove, which is on the no-load applied side, and an outer circumferential surface of an outer roller is set to satisfy \u03b41>0. When a change to the registration status of a service occurs, a notification message is transmitted to the application on the mobile device. Based on sensor utility values, the multiple sensors coupled to the device may be ranked. In certain embodiments, containers or closures have closure elements, which, upon being brought into proximity to each other, are drawn together and urged into alignment to engage locking members by magnets or other mutually attractive or repulsive elements, thereby providing a self-closing assembly. The top portion of the cover having means for receiving the plurality of structural support beams and the bottom portion having adapters for receiving the other ends of the plurality of structural support beams.