ugly as a mud fence

When someone or something is ugly as a mud fence it means they are very unattractive or displeasing to look it, so ugly in fact, nobody wants to look at it at all. By referring to a mud fence, it is simply a way to exaggerate the level of unattractiveness someone or something is. There are a variety of idioms that describes how unattractive someone or something is, as being ugly as a mud fence is simply another way to explain this.