Abstract: A cutoff device for pipelines has a unilaterally clamped flexible closure strip which can be unrolled onto a valve seat wall which is provided with through-flow openings. A roll is provided upon which the flexible closure strip is rolled and from which the strip is unrolled, the winding roll being so disposed as to be displaceable back and forth along the surface of the valve seat wall. The winding roll is tensioned so as to insure proper displacement of the flexible closure strip onto and off the roll and off and over the through-flow openings.