Hot Walls, Cold Walls (Article ID 131)
Abstract: Playing with hot and cold walls are consider table rules and not sanctioned by the National Mah Jongg League.
Question from a player: What is a hot and cold wall?
Answer from the NMJL: “We have no ruling on a hot tile. However, a good player would try to never discard a dangerous or obvious tile at any time or into the third or fourth exposure, thereby helping their opponents or giving mah jongg.”
Source: National Mah Jongg League Q&A 2007
Other answers from the NMJL:
“Please remember that we do not and never have sanctioned hot wall, cold wall or a pay game and therefore we have never made any official rulings on any of these operations as we do not approve of any of them.”
“We have no ruling for a hot tile or hot wall. That is strictly an individual game’s table rule.”
“No ruling for a “hot” or “cold” wall. A good player will not throw a dangerous or obvious tile at any time. Every pick and discard should be a challenge to the vary last tile.”
“No” hot” or “cold” wall. A good player will try and play defensively at all times. You should always watch and check the table and try and see what tiles are already discarded. We have no ruling on “hot” and “cold” wall.”
“We cannot give you hard and fast rules for defensive playing. This knowledge comes with experience. However, a good player never throws an obvious tile especially into a third exposure. As the saying goes, “you cannot mah jongg second.”
“Hot or Cold wall a good player never throws a dangerous or obvious tile at any time or into a third or fourth exposure, and every pick and discard should be a challenge to the very last tile on the wall. This is part of the fun.
Sources for other answers: National Mah Jongg League Q&A, (1967 page 5, 1968 page 4, 1972 page 5, 1975, 1970, 1980 page 3, 1981 page 3, 1982 page 3, 1993, 1997, page 5(last sentence left out), 1998 page 5, 2005, 2008, 2012, 2017) http://www.nationalmahjonggleague.org