Basics of screening
Screening is a process much like cheese grating but on a much finer level. A silk screen is stretched across a square wooden frame and nailed tight to it. The screen typically has a pour size between 180 to 120 microns. The smaller the microns the higher the quality but less the amount. The larger micron pours will result in larger sieved amounts but some leaf matter and branch trim will drop through. This will degrade the quality of hash that you smoke. Actually typical street hash is not nearly as fine or better in quality than the larger pour screen method.
The bud is placed over the screen and can either be manually dragged across the screen or rolled across the screen using a roller. Manually it is much easier if you are using smaller quantities of bud but for larger quantities another method should be adopted like the automatic tumbling method. A sheet of glass placed under the screen is the best way of catching the matter that falls through the screen.
After the process is finished the screen can be patted down to shake any powder that is stuck in the pours.