The Sacred Tile rules are used only in Japanese style Mah Jongg. It is a big reason why one of the main differences in play with other styles is the fact that a player’s discards are all neatly laid our in front of them so that there is now question who discarded which tile. If someone pongs or chis a tile that tile is set so as to point to the person who discarded it as well. Once you have discarded a tile you can not win by calling for that same tile. You can however win by drawing the tile yourself. The rule is important because this style of Mah Jongg is very defensive and your discarded tiles are used by the other players to determine what might be safe for them to discard and they give clues as to what type of hand you may be playing.
The rule becomes a bit more complex however when you are waiting on either end of a sequence. If you have discarded one tile from one of the ends you can not win by calling the other end tile. Both tiles become sacred tiles. This is often referred to as the 1-4-7 rule.
In this case a 2 crack or a 5 crack will give you a complete sequence and that is all you need to win. But early on you discarded the 2 crack so now both tiles are considered sacred and you must either draw it yourself or change your hand to win another way.
Another example to show some of the complexities follows here: You have already discarded the one dot. You are waiting to win on the end of a sequence. The one dot is sacred and you can not call it to win. You cannot also win on the a 4 dot or the 7 dot even though they would complete the 5-6 dot sequence. This is because the one dot could also satisfy the sequence. Hence another example of the 1-4-7 rule of thinking. Therefore you must sel-draw the tile in order to win the hand.
Sacred Tiling is especially dangerous when you are working a hand with a lot of sequences all in the same suit. You must pay careful attention to your discards as you work the sets of sequences. Not only is the rule 1-4-7 but some also refer to 2-5-8 and 3-6-9 because when working with multiple sequences you can see how easy a set can be completed by either of these tiles.
Sacred tiling also comes into play when you are waiting to win on either of two pairs to finish your hand. In the example below we are waiting on either the one dot or the nine bam.
You have already discarded the nine bam early on. So now both tiles are sacred because either would satisfy the winning hand and therefore you need to self draw the winning tile.
Sacred tile can be very complex. For example, you are waiting for a one bam in this hand because your way would be one through nine all one suit.
Your opponent then tossed a four bam which you passed on. You can be called for a penalty if the next person discards a one bam and claim Mah Jongg. Because the four bam would also have completed your hand but not in the way you wanted that made the one bam a sacred tile for that round.