Adhesion mechanisms with and without a defect for gripping and releasing objects are proposed, considering the adhesion between a semi-infinite elastic body and a rigid object with a sinusoidal surface roughness. These mechanisms are investigated theoretically. The total energy consists of the elastic term, the interfacial adhesion term, and the mechanical potential energy term due to the external pressure. The grip-and-release process is discussed in terms of the changes in the total energy and the contact width. The gripping stress can be expressed as a function of the elastic modulus. Using polymers with variable elasticity, the grip-and-release process is demonstrated experimentally and discussed in terms of the theory. (C) Koninklijke Brill NV, Leiden, 2010