Sven, Yes, that was the typical application of the pattress block in Britain as well, and seeing as the majority of old houses had masonry walls, they were used by the dozen.
By the way, what holds the cover of that switch in place? The equivalent "tumbler" switches here had either a round threaded boss in the middle so you just tightened the cover onto it, or they had two small screws above and below the toggle to secure it.
