Hit & Miss Ventilator

[whisky-dave]

I just had one of these installed.

I thought they were called air brick covers/ventilator, so why is this thing called a Hit & Miss Ventilator ?

[Graham.]

On Mon, 2 Oct 2017 06:39:00 -0700 (PDT), whisky-dave coalesced the vapors of human experience into a viable and meaningful comprehension...

Perhaps because they have a vague resemblance to a wooden structure such as this:

It's probably one of those terms that is better just to accept rather than rationalise.

[Robin]

"hit and miss" signifies the way they can be adjusted by sliding across the moveable screen.

OED has a definition:

Chambers's Techn. Dict. 417/2 Hit-and-miss ventilator, a ventilating device consisting of a slotted plate over which may be moved another slotted plate, so that the openings for access of air may be more or less restricted as required.

[Retro Futurist ...]

spot on .......also comes from drainage trap top piece cast iron covers which ventilate and at the same time stop debris dropping into the trap.......

[Matthias Czech]

Am 02.10.2017 um 15:39 schrieb whisky-dave:

My theory, that i will try to explain. (But will fail, because my English is not good, i am a Kraut) Look at this:

It is made of 2 identical sheets of metal with holes in it. The sheets can be moved parallel. If a hole in sheet 1 meets a hole in sheet 2: Hit! ->Airflow If a hole in sheet 1 meets a 'non hole area' in sheet 2: Miss! -> No Airflow

Hope, you see what i am trying to say.

[Graeme]

In message , whisky-dave writes

How boring. I thought there was going to be a David Jacobs connection.

[Bob Eager]

[Brian Gaff]

Because of the lining up or non lining up of the holes in the static and moving parts. Brian