Knight undoing This is simply meant to illustrate a fork it isn t intended to show all of the pieces and isn t intended to be a game It may have originally been intended only to show that But there s no reason not to use this situation to show the reader both one of the knight s advantages and one of it s weaknesses It s really a very good example of that which by the way the text adjacent to it describes In fact as I read the mentioned text I even expected that picture to show me that And frankly it s a better example of that weakness than the picture which shows a black knight its possible moves and a cornered knight with only two possible moves So I suggest either undoing your undoing or perhaps adding a new picture with the knight cornered after taking the rook there