pipe plug technical
pipe stopper

During one of these run-ins a pipe plug backed out.

Hubbard claims that "at that time core holes in the engine blocks were fitted with pipe plugs.

To test the drain, fit a vertical length of pipe plus pipe stoppers and fill with water.

Some generations back my husband's family included a respected bishop of the Church of England; among his heirlooms was a pipe stopper made of semiprecious stone and shaped like a gartered female leg, as in the Folies-Bergere.