For it to be a mathematical "knot", the edges have to be sewn together into form a knotted sphere. The trivial way to knot a blanket doesn't yield a trivial way

For it to be a mathematical "knot", the edges have to be sewn together into form a knotted sphere. The trivial way to knot a blanket doesn't yield a trivial way to connect all the edges without untying the knot.