29 C.F.R. § 779.334

The same principles apply in the case of sales of services for resale. A sale of services where the seller knows or has reasonable cause to believe will be resold is a sale for resale. Where, for example, an establishment reconditions and repairs watches for retail jewelers who resell the services to their own customers, the services constitute a sale for resale. Where a garage repairs automobiles for a secondhand automobile dealer with the knowledge or reasonable cause to believe that the automobile on which the work is performed will be sold, the service performed by the garage is a sale for resale. The services performed by a dental laboratory in the making of artificial teeth for the dentist for the use of his patients is a sale of services (as well as of goods) for resale. The services of a fur repair and storage establishment performed for other establishments who sell these services to their own customers, constitute sales for resale. As in the case of the sale of goods, in certain circumstances, sales of services to a business for a specific use in performing a different service which such business renders to its own customers are in economic effect sales for resale as a part of the service that the purchaser in turn sells to his customers, even though such services are consumed in the process of performance of the latter service. For example, if a storage establishment uses mothproofing services in order to render satisfactory storage services for its customers, the sale of such mothproofing services to that storage establishment will be considered a sale for resale.