url of this page: http://www.passingdb.com/articles.php?id=4

How to avoid collisions

Author: JiBe

Diagonal collisions: RH->RH and RH->RH (or LH->LH and LH->LH)

This type of collision is the most common and can happen in any pattern when both jugglers throw a crossing double at the same time.  To avoid them, you have to agree once and for all that crossing doubles will be thrown from the inside (close to the navel), whatever the pattern.

With collision

Without collision

Diagonal collisions 2: RH->RH and LH->LH

To avoid this, you have to agree that the person who throws with the right hand (R to R) will throw their pass from the outside (from as far right as possible) and the one who throws left-handed passes will throw from the inside (from the centre).  The diagrams on the left will give you an idea.  An example of a such a pattern is Brendan's Folly.
With collision
Without collision

Head-on collision: RH->LH and LH->RH

This type of problem is rather difficult to resolve and is only relevant to certain barbaric patterns (e.g. compressed Mesopotamia).  In theory, one must create imaginary corridors, the two jugglers slightly offset from one another (see diagrams); in practice, it's still hard to do!
With collision
Without collision