This picture shows a view of one of the Calstock bells in the 'up' position. The mouth of the bell is above the top of the picture and the crown is in the middle of the frame; the dark green coloured metal work, attached under the crown, is the headstock which sits between the wheel, visible on the left hand side, and the bearing on the right.
The bell is stable in this upward position because of the stay and the slider. The stay is the piece of wood with a square cross-section which is pointing down from the headstock; it is resting against the slider, with a slightly curved shape. The slider is pivoted under the wheel but as the name suggests, it can slide towards the front and back of the picture as the bell moves.
In full-circle ringing the bell turns through about 360° (a little less during ringing and a little more to set the bell). When the bell turns, the stay moves with it, touching the slider during every rotation and pushing it in alternating directions. This process is repeated until the bell is brought to rest with the stay against to slider. If the stay breaks through weakness or misuse the bell will turn freely which can be dangerous for the ringers below. Most towers keep spare stays or wood of the right cross section close at hand and the bells are inspected regularly to ensure they are safe.