Sometimes analysis requires deconstruction of a product, device or component. In these cases, unwanted material is carefully and systematically removed. Because the removal is destructive, careful documentation is required at each major step of the deconstruction. Specific procedures for deconstruction depend on the required information. "Tear down" is the deconstruction procedure used to gain an understanding of the overall structure of a product. "Failure analysis" is the procedure used to isolate and characterize failures.