I saw in the help section that one of the requirements of DC is "rigid package or 3/4" thick".  Can someone please clarify this for me?  Rigid means??? and 3/4" thick - can it be no thinner or no thicker?  I have a set of 3 small pb's to send.  Thanks for the help.

i didn't ever remember seeing that, so i went looking to try to find this.

here's what's in the help center:

Are there any requirements to use Delivery Confirmation?

Yes, provided that the package is at least 3/4 of an inch thick ("at its thickest point"), according to USPS Delivery Confirmation Regulations, and is being sent to a USPS-validated address.

If your package is NOT 3/4 of an inch thick, then it must meet ALL of the following criteria:

1. "rigid" (most books are)
2. be greater than 6" x 3" x 1/4 " in dimension
3. weigh more than 6 ounces

so to answer your questions, as long as the package is at least 3/4" thick, you don't have to worry about the others.  (and you can always add a couple of lightweight layers - perhaps a wadded up plastic bag - if it's not).  3 paperbacks - unless they're super-skinny childrens books - will probably be more than 3/4 of an inch, especially when wrapped.

rigid is the opposite of flexible, so most books will qualify.

Thanks!  The section I saw wasn't worded like that.