a pig in a poke
US /ə pɪɡ ɪn ə poʊk/
UK /ə pɪɡ ɪn ə poʊk/

1.
袋中之豬, 未經檢查的東西
something that is bought or accepted without first being seen or examined
:
•
Buying a used car without a test drive is like buying a pig in a poke.
不試駕就買二手車,就像買袋中之豬。
•
I'm not going to sign this contract without reading it first; I don't want to buy a pig in a poke.
我不會在沒有先閱讀的情況下簽署這份合同;我不想買袋中之豬。