Mipiringidzo yachitsulo yopunduka ndi zitsulo zazitsulo zokhala ndi nthiti, zomwe zimadziwikanso kuti nthiti zachitsulo, nthawi zambiri zimakhala ndi nthiti ziwiri zotalikirana komanso nthiti zopingasa zomwe zimagawidwa molingana ndi kutalika kwake.Maonekedwe a nthiti yopingasa ndi spiral, herringbone ndi crescent, Screw thread steel ndi chitsulo chofunikira pomanga zigawo zapamwamba kuposa kukula kwapakati, ndipo China imakhala ndi voliyumu yotumiza kunja chaka chilichonse.