what is it?

[belvedere]

A friend of mine shared this pic on FB, wondering what this is. Can anyone here help?

 

[alcorelli]

That is a valve lapping tool. A rubber cup goes on the pointed end and is pressed against the valve. The valve is installed with a very light spring.
When the handle is turned the valve will spin first one direction, then in the opposite direction.

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[Batscat]

It’s a rope chalk line.

 

[alcorelli]

Installed with a very light spring that will lift the valve when pressure is released.

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[belvedere]

Thank you!