Once the satisfactory design of a product or construction has evolved, and been detailed and checked, there is a need to specify quality characteristics against which to produce.

The quality of manufactured products is frequently dependent upon the effectiveness of the manufacturer's control of fabrication, inspection and testing operations. In consequence, manufacturers are responsible for instituting such controls over operation, processes and checking, as are necessary to ensure that their products conform to the specified requirements. Today, manufacturers are also often obliged to provide objective, verifiable evidence that they have carried out all necessary activities. This means that a supplier is expected to supply not only products and services but, in addition, proof that the product has been properly made and tested. A measure of assurance can be gained by (the customer) ensuring that everything necessary has been done to achieve the required integrity of each characteristic of the finished product. Thus, 'quality assurance'!