"Chas12" wrote:

I have no idea why people reply to innocent questions in this manner.
However, if you paid attention to my question you might have perceived that
it was sparked by frustration with all of the cheap closers available that
either get stuck in the open position, or never work as advertised. The fact
is the previous owner is an engineer, and why he would have installed a
non-closing vent is beyond my comprehesion.

Engineers don't have any great knowledge outside of their specialty.

Unless the guy was familiar with building and construction, he wouldn't
know what to do. Or the teenager working at the box store said "this
will work", and he didn't know anybetter.