It is not a stiletto, and so it is a sandal

Hello. So, taking a step back, I'd like to expand on Saussure's Structuralism.
Correct me if I'm wrong, but according to what I have learned, Saussure claims that signifiers signify through relationships of opposition. For example, this is a sandal. It is not a slipper, a stiletto, a pump, a running shoe,a moccasin, nor any other footwear. And because it is not any of these, it is a sandal. As much as this way of creating identity seems complex, and almost unnatural to the mind.. I recur myself making identifications in this way. For me, it helps to think of it as a process of elimination, because essentially, that's what it is. By eliminating all other shoes, you're left with one - the sandal. This might sound silly, but this "eliminating" process takes me back to high school where we were given multiple-choice questions and took part in a similar process of elimination, eliminating those answers that didn't pertain to the question being asked. Again, by eliminating those that oppose, you arrive at an answer; you find a shoe that "fits". Perhaps my way of thinking has some fault to it, but it's definitely helping me process some new things I have learned. Maybe it can help you too.