Products that pass the muster of this company get the UL symbol of approval. Underwriters Laboratories (UL) is one of the world's leading providers of product safety and certification testing services, performing more than 90,000 evaluations each year. Products that successfully navigate through its stringent tests are registered with the lab and can bear the UL Mark -- a widely trusted symbol for product safety and assurance. Nearly 20 billion products from 72,000 manufacturers bear the UL Mark each year. UL also offers commercial inspection and regulatory training services, as well as consumer safety advice. William Merrill founded the not-for-profit lab in 1894.