let's shake on it
Let us grasp each other's hand as a sign that we both agree to or on something, such as a deal or arrangement. A: "I'll give you $5,000 for your car." B: "Deal. Let's shake on it." Let's shake on it for now, and I'll draw up a formal contract when I'm back in Detroit.
Let's shake on it.
Let us mark this agreement by shaking hands on it. Bob: Do you agree? Mary: I agree. Let's shake on it. Bob: Okay. Bill: Good idea. Sounds fine. Bob (extending his hand): Okay, let's shake on it. Bill (shaking hands with Bob): Great!