The torsion pendulum at the heart of the apparatus to measure the gravitational constant. $G$ at the Bureau International des Poids et Mesures (BIPM) is used to measure the gravitational torque between source and test-mass assemblies with two methods. In the Cavendish method. the pendulum moves freely. https://hollandscountryclothinges.shop/product-category/zip-neck-sweaters/