I used to wonder what Isaiah meant when he wrote
2 Nephi 2:7 For the Lord God will help me, therefore shall I not be confounded. Therefore have I set my face like a flint, and I know that I shall not be ashamed.
Isaiah is writing Messianically here. The first sentence is clear enough, sure. It is an expression of the faith Christ had in his father. It was the image of setting one's face like a flint that I used to wonder about.
A flint is a very hard surface for striking against. The image is of a face that is immovable, not just like stone, but like stone that is particularly hard. It is a statement of Christs absolute undeviating determination to follow his father.
There is a little more to it. Setting one's face as stone is an image that is somewhat unpleasant. There is something here about the opposition and persecution Christ would face for his perfect determination to follow his Father. It isn't just an abstract determination, it is a determination that is made in spite of all the forces of hell and wicked men who strove against him. It is a knowing abandon of life as being easy, and of just getting along with everyone, because the adversary would never suffer wicked men to stand idly by instead of opposing and persecuting Christ for his determination to follow his Father.