A more thorough explanation:

The useful-article doctrine is a rule that states that a work of art that has a practical use and is also expressive may be eligible for copyright protection. This means that objects like bookends, lamps, and sundials can be protected by copyright if they have artistic value beyond their function.

For example, a lamp that is designed in a unique and creative way may be eligible for copyright protection because it is not just a functional object, but also an artistic expression. Similarly, bookends that are designed in a way that is aesthetically pleasing and unique may also be eligible for copyright protection.

It is important to note that industrial designs, which are designs that are created for mass production, are not eligible for copyright protection. Instead, they may be protected by design patents.

Overall, the useful-article doctrine allows for certain works of art that have both practical and artistic value to be protected by copyright, even if they are functional objects.