There are stones behind the shrines of rural houses, which affect Feng Shui?

There are stones behind the shrines of rural houses, which affect Feng Shui? After the stone is in the shrine, there are various situations. If it is flat, round or square, stable and solid there, it should be regarded as a treasure. If the oblique, pointed and prickly images are going to pierce the shrine or collapse to the shrine, they are not necessarily optimistic.