A traditional positioning system used with compasses in marble pointing to establish and transfer principal reference points between a model and the stone.
In the pointing demonstrations documented by Le voci del marmo, the cala is one of two traditional positioning systems used with compasses, the other being the centina. It is used to establish early capipunti and can be used to locate the most projecting or outermost reference point of a sculpture.
Etymology
Italian cala, literally associated with lowering or dropping; specialized workshop usage in the pointing system.
Sculptor Notes
The cala belongs to the geometry of traditional copying. Its purpose is not carving but the repeatable location of a measured point in three-dimensional space.
References
https://levocidelmarmo.sns.it/lista_video.php