How should I denote static classes in UML?

Question

So I did some research about how to denote static methods and classes in UML. I found on these two pages that static methods should be denoted by underlining them, but what

Answer 1

IMO static classes (like in C#) should not even be used in OO Design. A static class cannot be instantiated and thus is actually not a class regarding UML semantics.

You could mark the class as "leaf" (no subclasses) and add a constraint which does not allow non-static members. This would resemble the meaning of the C# static keyword.