~~~ only be (and will always be) a postcard.

EXAMPLE: Let's say you have a prepaid 10c postcard and want to use it on a package that costs $1 to mail, you cannot paste that postcard onto the packace (where postage is required) with 90c of additional postage on it because you are actually mailing two items; package and postcard. You will need the total proper postage for the package ($1) and the total current postcard postage in addition....

[A cost-saving tip] Let's say you have a sheet of postage stamps that got damaged to the point where you could no longer use them. Not to worry; as all you'll need to do is paste those stamps onto a sheet of paper and the post office will replace them, but only with the exact face pstage -- meaning that if you bring in 20 40c stamps to be replaced you can not ask for 10 80c stamps in return... you'll only get the 40c stamps (just as an example)... Thus the reason why all those full sheets of 2c and 3c stamps you see at antique shows and flea markets are sold at 20-30% below face... They can only be used on packages -- huge packages...