I have a simple question. I know that the objects that we work with in introductory physics are point particles. Thus, say we have a picture frame that is put on a wall. There is a wire holding it up, where the wire is attached to the top right and the top left corners of the frame. The passes through a nail so that the whole picture frame stays up. the wire makes a triangular shape with the picture frame. My question is how do we represent the tension forces on the frame in a free-body diagram if the picture frame is not a point particle, since the tension forces are acting on the corners of the frame.