Firstly, xyuas seb qhov saum npoo ntawm sab hauv thiab sab hauv lub tank yog zoo li hom polished, seb puas muaj nqaij doog, khawb lossis burrs; qhov thib ob, seb lub qhov ncauj vuam puas du thiab zoo ib yam, uas cuam tshuam txog seb qhov kev xav ntawm dej haus puas zoo nyob; qhov thib peb, seb qhov chaw sab hauv puas nruj, Seb lub ntsia hlau ntsaws phim lub khob cev; saib lub khob lub qhov ncauj, lub rounder zoo dua, tsis txawj kos duab tsis paub tab yuav tshwm sim tawm puag ncig.
