On packing of the lock which we buy to save the house, the property and other, is written "level lock".
But from what word there is this name?
No, not from the word "suvat" of course. And from very significant detail of the lock which is called a suvalda.
It is such metal plate of a difficult form with a cut in which the special ledge of a crossbar moves (a crossbar - the moving-forward detail). In the lock of these plates some, and their number can fluctuate. Suvalda are put in a so-called package and can move independently from each other perpendicular to the movement of a crossbar. Opening of the lock possibly only in that case when all suvalda adopt the relevant provision.
This mechanism (the truth, with small difference from a present design) was invented at the end of the 19th century in England.