This scope includes the CR-21, B-5, and all B-4R subclassifications. Work related to electrical, plumbing, fireplace protection methods, air conditioning methods, boilers, swimming swimming pools, spas and water wells should be subcontracted to an appropriately licensed contractor. This classification does not include work approved by the A-, B-, B-3, or residential scopes. This classification permits the licensee to put in and repair architectural and structural steel and aluminum materials common to the industry. This classification additionally includes reinforcing steel and area structure, chopping, meeting, and erection by welding, bolting, wire tying or riveting. Also included is the erection of rigs, derricks and associated substructures, and set up, service and restore of pumps and pumping gear.