Hereby I attached a photo of a Luopan I owned when I started to learn Fengshui seriously.
For practioner of Fengshui, this "Luopan" or Fengshui Compass is a must-have tool to help and determine the precise direction of a structure or object. In the world of Fengshui, the number of direction is no longer 8 but 24 directions. This translates to 15 degrees per direction. Interestingly, the Sun takes approximately 15.2 days to traverse a point. If you mark a series of 24 points on the ecliptic it creates a cycle of 365.25 days, which means that each degree on a luopan approximates a terrestrial day.
For advanced Fengshui practioners, they can also utilized I-ching with 64 trigrams incorporated in the Luopan in order to determine more information included Flying Stars.
In short, for those who would like to know their house or office's fengshui, first step is to use a Luopan to check the house/ office sitting and facing direction. Generally the market price for a professional luopan can be very costly because of the material use and integrations of different information in the Luopan and it can be used to avoid and block killing Qi from entering a house.
Anyway, you may also buy a low cost Luopan from roadside shop to measure 24 directions but it cannot be used to block killing Qi becasue the 8 trigrams (先天八卦 bā guà) is always intentionally located wrongly.