Welding of reinforcing steel or joints of reinforcing steel with other steel parts require the verification on suitability acc. to DIN 4099 of the executing companies to a notified body. As a notified body for metallic structures on the field of building supervision the GSI mbH with its branches and cooperating institutes checks within a verification procedure the preconditions on technical equipment and staff as well as the specific knowledge of the welding coordinator issuing the certificate if fulfilled.