We decided to tear the old wallpaper with my husband and glue new ones. In the course of our mini-repair, a small piece of plaster was falling off, which turned out to be a through hole leading to a neighboring apartment.
From the neighbor was such a plug that we easily got
Naturally, my husband and I arrived in shock, after this discovery. Already in the evening, when a neighbor came from work, our friendly "brigade" repairers went to visit him to "place all the points above I". But the neighbor is just something vague frowned about the technological holes. The husband could not stand and accused this "pervert" in all sins. Would you know how we sorry about it.
A bit of "walking", we learned that such technological holes in the panel houses are common. Using them, special round-lock locks, cling panels for installing them.
And the neighbor was invited to her dinner, where they apologized for a very long time.
A source