I need help setting up Scrog please

Hi there ive tried to look for best techniques to set up scrog with no real results and diagrams can anyone help please. also what are the main reasons for doing scrog?

Dystopia's PPP 250w VScrOG < BEST there is!

thanks good link

thanks roseman +rep

Scrog's pretty much putting a screen on top and letting your plants grow. then pulling the plant
back down and letting the smaller stems get grow and get more light so all of them grow evenly big [=

like this..http://www.growing-weed.org/wp-content/uploads/2010/11/scrog.jpg