Sitting on Zi, facing Wu
Sitting on Zi and facing Wu is the north-south axis most people picture first. For a house the back wall is to the north and the front door opens south. For a grave the stone has north at its back. Stand behind the stone and look back the way the ridge comes in: the hill behind you should rise in a steady slope and close, with no gap, road cut or saddle in line with the stone. A north back that falls away into a drain, a car park or an open field is a weak sitting, and no south facing makes up for it.
Tianlei, the rampart at the back
Tianlei, Heaven's Rampart, is the star our luopan sets on Zi: a wall that guards and holds. It is a common star, not one of the four nobles, so the Tianxing school does not use it to lift a site. We use it to check one. When the dragon enters from Zi, or a stone sits on Zi, we ask whether the ground behaves like a rampart: does the back close, do the arms on both sides wrap in, is the water held in front rather than running straight out. If the form does that, the star agrees with the ground. If the back is open and the water leaks, the name Tianlei changes nothing.
What this means on the ground
In a house, stand just inside the front door with your back to it and look out. Hold the luopan level at waist height, away from the door frame, keys and phone, and read it three times. At a grave, stand behind the stone and sight along its face. A reading of 180 means the site faces Wu and sits on Zi. Then see where the sitting falls inside the mountain. From 357 to 3 degrees you are fully on Zi. From 352.5 to 355 you lean on Ren; from 5 to 7.5 you lean on Gui. Each neighbour carries its own star, Tianfu on Ren and Tiandao on Gui, and a stone set on the line gets neither cleanly.
Common mistakes
The first mistake is true north. Zi is magnetic north, because the luopan is a magnetic needle. A phone compass set to true north in Vancouver or Sydney is off by more than ten degrees, which pushes a Zi reading onto Ren or Gui. The second is standing in the wrong place, reading from the pavement instead of inside the door with the door at your back. The third is copying north-south is best from a book and setting a stone to 0 degrees on land where the dragon comes in from the north-east and the water runs off to the north. The sitting is chosen last, after the dragon, the hills and the water.
Questions people ask
What direction is Zi on a feng shui compass?
Zi is due north, 0 degrees magnetic, covering 352.5 to 7.5 degrees. Ren lies to its left and Gui to its right. A stone or door sitting on Zi faces Wu, due south.
Is a house facing Zi bad in feng shui?
Not by itself. A door facing Zi sits on Wu, with south at its back. What matters is whether the back is solid and the water is held in front.
What does the Rat mean for Zi mountain?
Zi is the branch of the Rat, the midnight hour and the winter solstice, the most inward point of the cycle. On the ground that image means a closed, quiet back rather than an open one.
If your house or family grave sits on Zi, send Master Zhang three compass readings and a few photos of the back and front for a site reading.