A rampart on the north: what the name says
On the old star maps Tianlei is a ring of stars drawn as a walled camp. The school keeps the image narrow: a rampart guards, encloses and hides what is inside. Zi sits at 0°, the coldest point of the ring, and its star has the same temper: closed and still.
So a Tianxing master expects a Zi peak to look like a wall rather than a flame. A low, long, even ridge on due north, with its shoulders folding toward the site, matches the name. A sharp, leaning or broken peak on the same bearing does not, and the star does nothing to soften it.
How the school reads Tianlei on a range, a peak and water
The Cuiguan Pian treats dragon, cave, sand and water in four parts, each answered by the 24 stars, and Tianlei answers to Zi in each. When the incoming range enters from Zi, the school looks for a dragon that has gathered itself: a neck that narrows, then a head that swells and settles. If the ground does that, Tianlei confirms a sheltered, inward site. If the range arrives flat and loose, the star confirms nothing.
A peak on Zi is read as the wall behind the seat. Water from Zi should come slowly and be caught, not rush at the front. An ordinary star agrees with the landform; it does not lift a bad site one grade.
What this means on the ground
Find Tianlei on the Tianxing ring of the school's luopan, directly under Zi and under the needle's north. At a grave, stand behind the stone and sight along its face; at a house or shop, stand inside the door and sight outward. Keep steel and phones away from the plate and take three readings.
Then turn the sight to each peak and to the water mouth and note the mountain each one falls on. A peak between 352.5° and 7.5° sits on Zi, so on Tianlei. On a street, a solid, quiet building or a tree line on due north acts as a rampart; an open gap, a crossroads or a road running straight in does the opposite.
Common mistakes
The first is reading the star with a hiking compass or a phone app. Those give a bearing, often a true north bearing, which can land you on Ren or Gui instead of Zi. The second is to treat the name as a verdict. A rampart is an image of guarding and hiding, not a ruling that a site is safe.
The third is counting stars without walking the ground. If the north ridge is scarred, cut or hollow, no star on the ring fixes it. The fourth is measuring from a satellite map; the luopan needs the magnetic needle and your own eyes on the slope.
Questions people ask
What star is on Zi mountain in feng shui?
In the Tianxing school, Zi mountain at 0° due north carries Tianlei, Heaven's Rampart, an ordinary star read on the Tianxing ring of the school's luopan. The name means a wall or a camp: guarding and enclosing.
Is Tianlei a good or bad star?
Neither on its own. Tianlei confirms what the landform on the north is already doing. A well shaped northern ridge reads as sheltered; a broken or absent one reads as exposed, and the star does not change that.
Can I find Tianlei with a phone compass?
A phone set to magnetic north gives a rough bearing, so you know a peak sits near 0°. But Tianlei is a pairing on this school's luopan, so the phone tells you the mountain, not the reading.
To have the Tianxing ring read at a north backed site, book a site reading with Master Zhang or join the field course in Ganzhou.