An ordinary star on an elegant mountain
The rank belongs to the mountain, not the star, and the two should be kept apart. Ding is a heavenly stem, element fire, in the Li trigram with Wu on its left at 180 and Wei on its right at 210. Its opposite is Gui at 15 degrees. Ding is listed among the six elegant mountains together with Gen, Xun, You, Bing and Xin. An upright, whole peak on any of these is a good sand hill. Tianzhu adds the image of a pillar to that peak, a thing that props and steadies, and nothing more. A broken or leaning hill on Ding is still a broken hill; the elegant bearing does not repair it and the star does not either.
How the Tianxing school applies it
In Ganzhou we say heaven answers earth. The star ring is opened after the dragon has been walked, the water mouth found and the hollow fixed, and each part of the landform is matched to its star, the way the Cui Guan Pian does in its chapters on dragon, hollow, sand and water. For Tianzhu the match is simple. A guarding hill on Ding, especially one that stands square behind or beside the site like a post, is read as support, and the star agrees. Water arriving from 195 degrees is checked for the same thing. If the dragon enters the head from Ding, the pillar image fits a straight, firm entry. In every case the star describes; it does not promote.
What this means on the ground
Take the bearing from the site. For a grave, stand behind the stone, sight along its face and swing to the hill you are checking; for a house or shop, stand inside the door, back to it, and look out. Level the plate, wait for the needle, read three times, and keep steel away. A reading between 187.5 and 202.5 falls on Ding, and the slot above it on the star ring says Tianzhu. Note where in the slot it falls: near 188 it is a hair from Wu, near 202 a hair from Wei, and a stone set on the line between two mountains is what the trade calls straddling, to be avoided. In town, a solid mid rise block on this bearing can serve as the pillar; a gap, a demolition site or a leaning crane cannot.
Common mistakes
Reading the star off a phone app. The app has no star ring and is usually set to true north; with the variation found overseas a true north reading can move a hill from Ding onto Wu. Treating Tianzhu as a verdict. Pillar, support, steadiness are the name's imagery, not a statement about anyone's career or health. Counting elegant mountains and stars before looking at the hill itself. Measuring from a satellite image, where neither the door nor the stone can be sighted.
Questions people ask
What star sits on Ding mountain?
Tianzhu, Heaven's Pillar, at 187.5 to 202.5 degrees, south by south west. An ordinary star. Ding is one of the six elegant mountains, which is why a peak on it is valued.
Is Ding one of the six elegant mountains?
Yes. The six are Gen, Xun, You, Bing, Xin and Ding. The rank is about sand hills and incoming water on those bearings, not about the facing.
What does Heaven's Pillar mean in feng shui?
The name means a pillar that holds up the sky: support, steadiness, something to lean on. On the ground it is an image for a firm, upright hill on Ding. It is not a forecast of anything.
Have Master Zhang check which bearing your guarding hills stand on, or come to a Ganzhou field course and read the star ring on a real hillside.