Cov tshuab dov hlau muaj nqis yog cov chav uas cov txheej txheem tsim hlau tshwm sim. Thaum lub sijhawm no ntau yam khoom siv hlau tau dhau los ntawm ob lub yob, lossis cov khoom siv tuav cov khoom siv. Lo lus "dov" yog cais los ntawm qhov kub uas cov hlau tau dov. Goldsmith dov mills ua haujlwm los ntawm kev siv ntau lub rollers los tswj cov khoom siv ntawm cov hlau ntawv. Hauv kev ua cov ntawv kub, lawv muab cov tuab thiab sib xws rau cov hlau kub nyiaj tooj liab uas lawv siv. Cov tshuab Goldsmith muaj cov rollers uas zawm thiab nias cov hlau ntawv thaum nws dhau los ntawm lawv.

Hasung muaj ntau hom tshuab dov hlau, xws li tshuab dov hlau kub, tshuab dov hlau thiab ntawv, tshuab dov hluav taws xob thiab tshuab dov hniav nyiaj hniav kub thiab lwm yam. Cov tshuab dov hlau yog cov chav uas cov xov hlau loj dua hla dhau ob lub rollers nrog qhov. Qhov loj me ntawm cov xov hlau tuaj yeem hloov kho raws li qhov yuav tsum tau ua. Cov tshuab kos hlau nrog ntau lub pwm los ntawm kev txo cov xov hlau loj ib zaug ib zaug. Txij li qhov siab tshaj plaws 8mm hlau mus rau qhov tsawg kawg nkaus 0.005mm lossis txawm tias me dua.

Ua ib lub tuam txhab tsim cov tshuab dov kub uas muaj nqis heev, Hasung tau koom nrog hauv kev lag luam tshuab dov, thiab cog lus tias yuav muab cov khoom siv dov kub zoo rau cov neeg siv khoom, cov tshuab dov kub thiab lwm yam khoom thiab cov kev pabcuam.