Abstract: A sealing element seals a gap which may be formed between two components that are movable thermally relative to one another. Each component has a component groove located one opposite the other. The sealing element is directed along a center line, in a cross-section essentially perpendicular to a main line, and has a first end, a second end located opposite the first end and a toothed middle region located between the ends. The sealing element is suitable in particular for sealing off a gap between guide blades at high temperatures in a gas turbine plant for the purpose of preventing a gas flow out of a cooling-gas region into a hot-gas region. A gas turbine plant is provided with the sealing element for sealing the gap.