The invention pertains to a method and apparatus for clamping and subsequently machining a disk- or ring-shaped workpiece, wherein the workpiece is set down on a contact surface of a contact member made from elastomeric material. The liner plug may be releasably attached to the canister via a first release mechanism. The merchant has a constantly searchable presence and has feedback about the success of other programs in related businesses and geographical areas and the analytics of the users of the program for continual updates of the special offers in real time. The first wall may be planar segments, or may have a circular cross section.