What happens if you try to tie a (mathematical) knot using not a string or yarn but a stiff, springy cord such as hardened steel wire or basket reed? This is not an easy task, but, if you succeed, you will find that certain knots will settle into very interesting, stable 3D configurations and will spring back to these shapes when deformed. Focusing on two well-known families of knots, we identify the ones that have this property and demonstrate some practical methods for tying them into kinetic decorative objects such as self-tightening bracelets.