A method and apparatus is provided which secures the lid of a processing chamber in abutting engagement with the walls of the chamber to form an airtight processing environment and which provides for the release of pressure within the chamber in the event of a sudden change in pressure such as an over pressure excursion. The method and apparatus generally comprise a clamp member having a base portion for mounting the clamp to a first surface, a contact portion for contacting a second surface and maintaining a desired relationship between the first and second surfaces, and a deflecting portion which allows separation of the first and second surfaces to relieve pressure behind the first or second surface and return to the desired relationship between the first and second surfaces.