The sunken bone can be found at the bottom of a scale. To make scales grounded, you will need to find a sunken bone and place it at the bottom of the scale. Once you have placed the bone in the scale, you can then add your other objects to create your weighed object. Make sure that the object is touching the bone in order to get an accurate reading. If the object is not touching the bone, your scale will be ungrounded and you will not receive an accurate reading.