Perhaps if I'd used the proper name what I said may have been clearer. The correct name is hemp rope or plumber's rope but I don't often have that around (not being a plumber) so I use the next best thing available Hessian fabric or its rope equivalent).

Here are some photos: https://www.bunnings.com.au/enduraseal-1m-plumbers-hemp_p012...

https://waropes.com.au/twines/plumbers-hemp/

You wrap the hemp fibers around the threads that have been brushed with linseed oil paint then apply a little more paint to the hemp and then mate the couplings together. This sealing technique has been around at least for several hundred years if not longer.