A closure system comprising a three-dimensional structure having an opening to be closed, and a cover for attachment onto said three-dimensional structure to close said opening, said cover comprising: a top wall which is deformable in a bistable manner between a first state which is cambered in the direction of attachment and a second state which is cambered opposite to the direction of attachment; and an annular edge portion having a larger outer circumference in the first bistable state than in the second bistable state and therefore being adapted to effect a clamping attachment of the cover to a wall region of the opening in which, in the closed state of the closure system, the edge portion of the cover presses in the first state at a contact point from inside against the wall region, characterized in that the three-dimensional structure is produced from a material which is, at least at a predefined location, so flexible that a force (F 4, F 5, F 5 ', F 5 ") acting transversely to the direction of attachment on the wall region of the opening from at least one and preferably from two opposite outer sides onto the at least one predefined location is transferred in such a manner that the cover is caused to snap from the first bistable state to the second bistable state. a three-dimensional structure having an opening to be closed, and a cover for attachment onto said three-dimensional structure to close said opening, said cover comprising: a top wall which is deformable in a bistable manner between a first state which is cambered in the direction of attachment and a second state which is cambered opposite to the direction of attachment; and an annular edge portion having a larger outer circumference in the first bistable state than in the second bistable state and therefore being adapted to effect a clamping attachment of the cover to a wall region of the opening in which, in the closed state of the closure system, the edge portion of the cover presses in the first state at a contact point from inside against the wall region, characterized in that the three-dimensional structure is produced from a material which is, at least at a predefined location, so flexible that a force (F 4, F 5, F 5 ', F 5 ") acting transversely to the direction of attachment on the wall region of the opening from at least one and preferably from two opposite outer sides onto the at least one predefined location is transferred in such a manner that the cover is caused to snap from the first bistable state to the second bistable state. a top wall which is deformable in a bistable manner between a first state which is cambered in the direction of attachment and a second state which is cambered opposite to the direction of attachment; and an annular edge portion having a larger outer circumference in the first bistable state than in the second bistable state and therefore being adapted to effect a clamping attachment of the cover to a wall region of the opening in which, in the closed state of the closure system, the edge portion of the cover presses in the first state at a contact point from inside against the wall region, characterized in that the three-dimensional structure is produced from a material which is, at least at a predefined location, so flexible that a force (F 4, F 5, F 5 ', F 5 ") acting transversely to the direction of attachment on the wall region of the opening from at least one and preferably from two opposite outer sides onto the at least one predefined location is transferred in such a manner that the cover is caused to snap from the first bistable state to the second bistable state.