A friend is restoring the original wood windows on his house (at
least 50 years old). It appears as though most of them don't have
sash cords. I don't mean broken - like they never had sash cords to
begin with.

On a few of the windows, they have a swiveling hook thing on the
outside. I've been told that this was used to hold the bottom sash
in place when opening the window (see photo).

Is this correct? What do you call this thing?? And where can you find them??

Any help would be greatly appreciated! Thank you!