In violin making and bow making, the movable lower part in which the hair is used is called the nut. The nut used to be made of wood, ivory, bone, tortoiseshell or horn. Ebony, snakewood or rosewood are used as wood species, whereby ebony clearly predominates. The metal parts of the modern frog such as ferrule, liner and heel have been developed and installed over the years in order to increase the lifespan of the frogs. Here you can find a cross-section of a modern frog including mechanics on our site.