Cloth on book spine?

Hi Gurus,

I'm new to this widely informative forum. Thanks so much for sharing your vast knowledge and experience so us new guys wouldn't have such a hard time making it in this business.

I'd just like to ask what's the cloth between the cover and the book block spine in hardbound books? I believe this is called crash (?)

If any of you would be kind enough to refer a supplier of this, I'll very much be grateful.

Thanks so much!

Dixter