Half a foot of land is now mainly used for size measurement related to geomantic omen. If it is the size of the door frame, Lu Banchi should measure the height and width of the door leaf. Plastic steel and aluminum alloy doors and windows are also the widest parts to measure! I hope it's useful to you:)
In addition, there are rulers in Lu Banchi now, but in China, I suggest you use city rulers and CM units. Note that the good and bad luck of the two are completely different and need to be chosen according to the owner's region.