Today, a few words about special metal details that we can find on historic buildings (and not only). Survey benchmark is a permanently stabilized point of geodetic network. They are used for geodetic measurements. In the past they used to be placed on old buildings, like churches - the best were already stabilized facilities that completed the settlement process. Many of these marks are so old that already can be recognized as monuments. Some of them can still be used as a part of contemporary geodetic network, some of them left only as historical curiosity. These details are often forgotten when renovating historic buildings. They are often thoughtlessly covered with paint but we should keep them and expose as integral part of the buildings' history.
Sometimes we can also observe new local measurement points on historic buildings, which are used to check whether a given object is moving, e.g. as a result of construction works carried out nearby.