on the knocker
立即、确切地支付或做某事
口语·强调立即支付或现金交易
英文释义
to pay for something immediately or in cash when it is delivered or completed
例句
He paid for the car on the knocker, no financing needed.
典故来源
可能源于上门推销员敲（knock）门后立即交易，强调当场付现。