11.   That help creates a tight seal between the sink and the plunger.

12.   The bushy lip, it turned out, prevented a tight seal between his mask and his face.

13.   The regulations say facial hair interferes with a tight seal for respirator masks used by ambulance personnel to guard against communicable diseases like tuberculosis.

14.   This assures a tight seal.

15.   This cycle is repeated until finally the flapper does form a tight seal.

16.   The outer chamber of the air lock is depressurized before the astronauts step out, making a tight seal essential.