Try the technique before you buy with a DIY alternative. Roll a sheet of black card into a cone and place a strip of black or gaffer tape along the seam to hold it securely in place.
在买之前先自己DIY一个，把一张卡纸卷成圆锥型，用电工黑胶粘牢。
2
You should see the flash-card screen roll down from the top right corner, stay for a bit, then roll back up.
应该可以看到 flash-card 屏幕从右上角滚下，停留一会儿，然后又向上滚回。
3
The pattern desired is transferred to a series of perforated CARDS or a roll; one card is required for each shedding and placing of a filling pick.