For some readers, these are a fact of everyday life – for others, well, it is frankly surprising how many Americans have never heard of nor seen this simply ingenious style of window that this author lived and worked with while growing up partly in Germany (their point of invention within Europe).
Almost a secret in the United States, the dual-action premise is simple: twist the handle one way and the window swings all the way open like a door (some, in fact, are used as such – a framed glass window + door). Turn the lever the other direction, pull toward you and it opens inward to let in some air but locks at an acute angle.
Essentially, there are two separate hinge systems in play – turning the handle releases one part and locks into the hinges of the other, switching from a side swing to a vertical tilt (though, if you aren’t careful, you can trick the system and free both sets at once).
Humblest apologies to those for whom this is old hat, but for everyone else: these really are the ultimate window systems. And some companies like T&T Windows have brought them to the US and Canada for anyone interested in learning more or buying some.