John,
The painter's shield is one of those thin plastic boards that Home Depot sells to do-it-yourselfers to block off edges, like baseboards, when painting walls. I think it's a piece of polyethylene plastic. The shield isn't actually attached to the fender flare, but is zip-tied to the roughly "V" shaped truss that stiffens the fender. Nick didn't have room to get the proper perspective when he took the picture. The shield fits inside and forward of the edge of the fender lip. If I can get some time Monday or Tuesday, I'll take it off and get some pictures of it with some measurements, so you'll have a better idea. As you can see from the picture, it completely shields the filter from debris, mud, or snow. It's very simple and easy to make and install. One of the guys at the Sacramento get together thought it would be a good idea to put one on the other side just to keep crud from building up inside the fender. I think he's right.
TC