The 24 Mountains
"What is N1 or SW3?"
In Eight Mansions, houses have one of eight facing or sitting directions. They are north, south, east, west, north-east, south-east, south-west and north-west. Each facing spans 45 degree. For example your house is deemed to be facing north if it has a facing direction anywhere between 337.5 and 22.5 degrees. Others like Zi Wei Feng Shui delineate houses into 12 different facing of 30 degrees each.
Most others like Xuan Kong Fei Xing (Flying Star) or San He delineate into 24 facing directions of 15 degrees each.
There are 4 cardinal (north, south, east and west) directions and four inter-cardinal (north-east, south-east, south-west and north-west) directions. They make up 8 directions or sectors of 45 degrees each. Each of these sectors is further divided into three sub-sectors of 15 degrees resulting in 24 facing directions of 15 degrees. In Feng Shui terminology each of these 24 sub-sectors of 15 degrees is known as a mountain, hence 24 mountains.
Let's take the north sector which spans 45 degrees from 337.5 degrees to 22.5 degrees. Sub-divide this into three equal sub-sectors of 15 degrees span and call them N1, N2 and N3. In ancient Feng Shui text they are labeled Ren, Zi and Gui. N1, 2 and 3 are however much easier to remember.
Do the same to the other sectors and label them according e.g. NE1, NE2, NE3.
Please click the link below to view the 24 mountains with the traditional names and modern equivalent.
If you house has a facing direction of 182 degrees, it is said to face S2 or Wu. In traditional speak it is known as a house that is "Facing Wu, Sitting Zi". For me it is much more intuitive to simply say facing S2. The choice is really up to you.
In addition to being known as mountains, the 24 facing directions are also known as dragons. The ones in the middle or the ones with the suffix 2 e.g. N2, NE2, E2 etc are known as the "Heavenly Dragon".
The ones to the left of the center or those with suffix 1 e.g. N1, NE1, E1 etc are known as the "Earthly Dragon" while the one to the right or those with the suffix 3 e.g. N3, NE3, E3 etc are known as the "Human Dragon".
It pays to commit this to memory as it will aid your understanding when reading translated versions of older text.