I have always thought the line was what they have to land with their hands on the other side of. Not completely sure, though

. As far as deductions go, I really don't know. I was talking to a coach once about the level 4 vault and commenting that it seems hard to tell if a vault is good or not, and she told me all the different deductions that can arise, and I was very surprised, especially on level 4

! Who would have known - it seems like a cut and dry skill

!