East rolls two dice then counts the stacks of tiles (a stack includes both the top and bottom tiers of the wall) from right to left according to the sum rolled on the dice. After counting, East creates a gap or “break” in the wall at that point.  The wall to the left of the break is pushed to the center of the table at a 45-degree angle.  The tiles to the right of the break remain where they are because they are a continuation of the last full wall to the right in front of Player 2. As the National Mah Jongg League states in a letter to a player, “To move them to the LEFT would be providing a break between the 3rd wall and the remainder of East’s wall. We have seen this lead to issues where players do not realize there are still tiles to be played.” Refer to the illustrations below:

Source: Mah Jongg Made Easy 2020, page 10 (illustration only), Letter to a plyer 2/12/2019