Here is what the rule states on page 22 in the 2018 rulebook:

An offensive or defensive player on the field of play, including inside the free blocking zone, shall not initiate a clip or block below the waist of an opposing player.

The key to this new rule is that neither the Offensive or defensive player may INITIATE a block into the knees.

Defensive players that want to grab grass, hold their ground or whatever you want to call it - may do this but they cannot go into the offensive players knees.  If there is a question on whether the defensive player went into the offensive players knees the officials will be instructed to call the penalty.

The same can be said of the offensive player going to into the defensive players knees - some have asked about crab blocking. If there is any question about the offensive player going into the defensive players knees the officials will be instructed to call the penalty.

Officials will be looking for blocks into the opponent’s knees.

At the end of the day, this is going to be a judgment call by the officials, so if you have film during the scrimmages or the first few games of a block below the waist (or lack there of) that you do not agree with, please send me the video and we will review.