Sell a pig in a poke.

猪装在口袋里卖。

Never buy a pig in a poke.

千万别买袋子里的猪。

My brother bought a pig in a poke.

我兄弟做了次冤大头.

Buying land by mail is buying a pig in a poke; sometimes the land turns out to be under water.

邮购土地是一种盲目的交易；有时候购买的土地竟是在水底下。

I want to see the tennis racket before I agree to the price. I don't want to buy a pig in a poke.

我想先看看网球拍然后才能接受这个价位，我可不想胡乱买东西。