The invention relates to a method and device for maintaining a separately-determined trajectory and securing an electrode or other such placed object through a bone, such as a skull, while also covering the aperture. The device includes a base and an engaging-disengaging butterfly with inner sleeve for temporary engagement of the base and sliding screwdriver for engaging the base or butterfly inner sleeve, depending upon desired function. The base's lower portion engages via threads the bone, while maintaining previously determined trajectory； the upper portion engages the butterfly to continue to maintain previously determined trajectory electrode trajectory； a feature grasps a passing electrode in a given position； the electrode grasp from the butterfly can be then released, the base screwed in to final position, and the butterfly disengaged by unscrewing it from the base.
