expression, godan verb (-su)
make sure of; drive a wedge
Idiomatic expression meaning to take precautionary measures to ensure something, often by giving a warning or reminder. The literal meaning is 'to drive in a wedge'. Rare term.
彼に遅れないように楔を刺しておいた。
I made sure to warn him not to be late.
契約の前に、条件を確認して楔を刺す必要がある。
Before the contract, we need to double-check the conditions and make sure.