The expression "ringing the curtain" refers to the closing of a theatrical performance. While this phrase is commonly used, there are many synonyms that can be used in its place. Some of these include "lowering the curtain," "dropping the curtain," "closing the curtains," and "bringing the curtain down." These phrases all convey the same idea of bringing a show to an end, and can be used interchangeably based on personal preference or the context of the situation. It's important to note that while these phrases may have subtle differences in connotation, they all serve to signify the end of a performance.