An important mechanism in slow infinitesimal deformation on grain scale that is limited to the margins or boundaries of the grain is known as Coble creep. It is like grain boundary sliding but involves also inter-grain diffusion. It is a function of temperature, the shear modulus and several other constants but most important being the diffusional constant. It works in conjunction with Nabarro Herring creep. In effect it is orderely movement of dislocations.