Sentences: Book Donations to Prison Libraries and Juvenile Detention Centers discussion

It can save you some money to tape up your box before you go to the Post Office. You're not required to show the contents of the box of books when paying for the media rate (though it is subject to later inspection, just to make sure you didn't mix in non-media contents). The Post Office will supply tape when you ship Priority Mail, but not when you're asking for the media rate. So if you bring an open box and need to tape it up when you get there, you may have to buy a roll of tape from the Post Office.

Thanks for the tip!