You can determine the shape of your partner's hand by looking at the length and width of their fingers and the shape of their hand as a whole. Round, square, oval, and elongated are some of the most common hand shapes. You can also note anything that makes them stand out, like big knuckles or thin fingers. If you are unsure, you can always seek the advice of a jeweler who can assist you in selecting a ring that will look beautiful on your partner's hand.