the world > space > relative position > closed or shut condition > that which or one who closes or shuts > [noun] > that which closes an aperture > material or composition used for > for specific purpose (2)
(a) any material used for filling the space between a piston head and the cylinder within which it moves, so as to prevent steam, air, etc., leaking…
watertight packing used in an oil or gas well, typically to seal a well after the withdrawal of a drill or to seal the gap between a drill pipe…