欧洲人磨刀/剑:一手拿刀,另一手用磨刀石,中国人把磨刀石固定一个台阶,用双手磨刀。)(Europeans sharpen knife/sword: one hand holding knife, while the other hand using sharpen stone. Chinese fix the sharpening stone one a stage, using both hands to sharpen knife.)
https://www.youtube.com/watch?v=XM8IQ90v_MQ