Silk screen can be used to sieve the trichomes into a fine kief which can be pressed into hash.
Art supply or hobby shops sometimes stock it....call a few in your area and find out.
He's probably using the mainstream how to make hash video which says to get a silk or mesh screen. I remember the guy say use the screen that t-shirts are printed on.Can't you make your own?
Nothing. It helps for making hash though...What does this have to do with growing pot?