Cracking walls and walls of buildings can be a significant threat to users and the entire structure. They always require proper repairs. Before that, however, it must be ascertained how quickly the cracking process is taking place. For this purpose, several small panes are glued with gypsum plaster in several places on the visible scratch. As a crack begins to enlarge, it will be easy to determine the size and speed of the crack expansion, because the glass will peel off one cake and move over it.