Crotal bells or rumble bells were used to warn other horse drawn vehicle users that another vehicle was approaching. They came in many sizes from a small 1 inch version to bells that were many inches across. They were either hung on a small leather strap or an iron harness bracket above the horse's collar. On larger vehicles, such as delivery wagons, they were driven into the wooden frame of the wagon. Often refered to as sleigh bells, these were used year-round.