In that case get the script - it lets you snap the pivot to certain boundaries, or position it by numbers. The skeleton, like other figures, was rigged in Poser - even with the centre-setter to fix the pivot point you still won't be able to make a true figure, and you certainly won't be able to have the joints flex the way those in one of the human or animal figures, or a set of clothing, do. (We have been told that rigging tools for D|S are coming, but not very soon.)