States that if your ball enters a lateral hazard, you can drop within 2 club lengths of a point on the opposite margin
of the hazard equidistant to the hole from the spot where the ball last crossed the margin of the hazard.
The drop just can't come to rest nearer to the hole.
This rule was used in the recent St Jude Classic by Rory where after using this rule and dropping his ball, he had a clear line of sight to attack the pin compared to if he had dropped the ball 2 club lengths at the point of entry to hazard.
For more illustration, you may wish to refer to this month's Golf Digest.
Found this enlightening and sharing it here.....