How do you measure "Manos"?

Or, for that matter, WHAT IS a Mano?

When neither Jerra, nor I could shift a couple of screws on the water
not-heater, I decided to try my favourite fettler.
May be just as well we couldn't shift them.
Conclusion:-
I'll not employ the "technical term" employed, but leave it to your imagination, bearing in mind it was declared dead.
The upshot - Sorted, but "I haven't used the pressure tester yet."

Being out of the house , for one of my periodic meals somebody else made, I thought I'd b nip up there "for the crack".
Behold the "Pressure tester" which all my life, from 2ndry school on, I've known as a "Manometer", but never known just exactly what a "Mano" was which was being measured.
So, again, being me. I looked.

"Instrument for determining and indicating the elastic pressure of gases or vapours, 1730, from French manomètre (1706), said to have been coined by French mathematician Pierre Varignon (1654-1722) from Greek manos "thin, rare; loose in texture, porous; scanty, few", "small, isolated") + -mètre (see - meter). Related: Manometric; manometrical; manometrically."

So - we appear to be measuring lack of pressure, rather than pressure, despite the fact in will measure in both "directions".

Only goes to prove it does not need to be high-tech to work, hence the way many doctors still prefer a Sphygmomanometer (which I've just spelt without checking {grins} ) over the modern, digital variety.

It's entirely possible you'll get to see the offending mechanism upon the morrow.
;¬)