Fig.: to buy something without previous examination or knowledge

Buying a used car without test-driving it, is buying a pig in a poke. It may easily turn out to be a lemon

Comperare una macchina usata senza prima provarla è proprio comperare la gatta nel sacco. Può facilmente rivelarsi una carretta

I don't like to buy from the Internet because what you see on the screen could turn out to be a pig in a poke. You need to see and touch the real thing before buying it

Non mi piace fare acquisti da Internet perché quello che vedi sullo schermo potrebbe rivelarsi come la classica gatta nel sacco. Bisogna vedere e toccare con mano quello che si vuole comperare

In older days, con-men at county fairs would put a cat in a "poke" (a small sack) and, claiming it was a suckling piglet, find someone who was simple enough to buy the "pig" without even looking into the bag, because everyone knew how hard it would be to catch the piglet if it got loose. A canny purchaser, however, might refuse to buy without an examination of the contents, and, by opening the sack, would literally "let the cat out of the bag"