I would not recommend using a mash screen like shown above. What happens is during lautering the wort will channel down through the grain to whatever the "exit" is. When you use a mash screen like above you are essentially creating a "V" shape in your grain bed. So you end up with heavily rinsed grain closer to the mash screen and un-rinsed grain on the outside. You'll get pretty crappy efficiency that way and may even extract tannins and such that will create a grainy taste in your beer. Spend the extra few bucks and use a false bottom or build a manifold that covers a greater surface area in your mash tun.