What is a saddle sleeve?

A "saddle sleeve" is not a commonly used term. It's possible it's a slang or regional term for something else.

To understand what you might be referring to, I need some more context. Could you please provide:

* Where did you hear this term? (e.g., a book, a conversation, a website)

* What was the context? (e.g., what were they talking about when they mentioned a saddle sleeve?)

* Are there any other details? (e.g., what was it made of, what size was it, what was it used for?)

With more information, I might be able to figure out what you're looking for.