Feng Shui says that nails can be put, does that mean adding to the blockage?

This is misleading. According to Feng Shui, the owner of the mountain is the owner of wealth, so the house will have a backer first, that is, there will be descendants. The so-called throwing nails means hurting others and hitting nails. For example, when the owner is too stingy and harsh on the craftsman when making a new house, the craftsman's heart is unbalanced, which will harm the owner and nail a nail in the wall, which will lead to bad things for the owner to move into the new house.