Black Box Explains...UL® Listed carts.
Underwriters Laboratories® (UL) is a nonprofit organization that tests and develops safety standards for a variety of products and manufacturers.
If a product—a cart or similarly framed structure, for example—successfully completes a series of safety tests, it is granted a UL® listing verifying it has met an industry standard for acceptable levels of performance.
Obtaining a UL® listing is particularly desirable because carts and storage devices are used in schools and other institutions where safety is paramount.