What do you mean, two-faced? What does a duplicitous person do?

Two sides: male side and female side; The positive side is a smiling tiger, and the negative side is a sinister face, which is the so-called bait hides the hook.

Three knives: soft knife, hard knife and dangerous knife; Soft knives kill people without bloodshed, hard knives kill people without mercy, and dangerous knives are hard to prevent; It is difficult to deal with people who are both soft and hard, and who are insidious and kind.

Metaphor has ulterior motives, face to face and behind.

The performance of two-faced people: one is in front and the other is behind; What you say is human, but what you do is a ghost.