Nrog rau txoj kev loj hlob sai ntawm kev lag luam kho kom zoo nkauj, lub sij hawm thiab cov neeg tau muab tso rau pem hauv ntej siab dua, zoo dua thiab ceev yuav tsum tau kho kom zoo nkauj.Ntau yam khoom siv kho kom zoo nkauj tshiab, txoj hauv kev thiab cov qauv kuj tseem ua raws thiab tsim kom muaj zog.Nyob rau hauv xyoo tas los no, cov khoom siv kho kom zoo nkauj nrov heev 'pob zeb slab' tau los ua.Cov ntaub ntawv zoo li no yog khi rau qhov sib txuas ntxiv thaum nws los txog rau ntau txhiab tsev neeg.Raws li lub pob zeb phaj yog cov khoom uas tau nias rau hauv ib daim ntawv los ntawm kev kub siab, thov tsis txhob txhawj txog nws qhov hardness, vim hais tias cov khoom ua los ntawm kev kub siab nias yog cov khoom zoo heev, thiab cov tuab hauv qab ntawm daim ntawv kuj muaj cov kev xav tau ntawm kev tshawb fawb, tsis txhob hais tias qhov thicker qhov zoo dua, yog li thov ntseeg cov neeg tsim khoom cov lus qhia thaum yuav khoom, vim lawv yog cov neeg tshaj lij tshaj plaws.