Three Advantages in a Bind
Regarding blade binds, there are three criteria that determine whether or not one is stonger in a crossing of swords. You have the advantage if
  •     your blade is over and on top of  his blade.
  •     your edge is turned against his flat.
  •     the strong of your blade is in the weak of his blade.

Not all criteria have to be met simultaneously to win a bind, though. For example, if your blade has superior leverage (your strong in his weak) and at the same time your blade is crossing over his, you will be stronger in this bind even if your flat is turned against his edge.

You may want to watch my spear play videos which explain the concepts in more detail: Find part one here  and part two here .