What are those thick cardboard escalopes you use to mail textbook in called?

I don't know if I explained it right. But they look like brown escalopes the size of a textbook probably 11' x 8' and their very sturdy, and you mail textbooks in them.





Does anyone know what their called?



where can I find them?What are those thick cardboard escalopes you use to mail textbook in called?
a Box you can get them at a post office,What are those thick cardboard escalopes you use to mail textbook in called?
You can take a piece of cardboard (from an old box) and wrap it around the textbook. If the book is hardcover, you will have no problem. if paperback, then it only works with small books. Do not use this method for 8.5x11 paperback books, it will damage them.What are those thick cardboard escalopes you use to mail textbook in called?
Boxes?

Padded envelopes?

You can get either at the Post Office and at office supply stores.



What's an escalope?