every time i mate two parts together by selecting a face from each part, not only do the two faces mate together but the second part will move to the first part to the point at which i selected the face of the first part. this is something that's been happening for quite a while and most of the time its helpful, but for what i'm doing right now it's annoying as F! is there a way of turning this off or do i just have to deal with it?