I had to build one, or more correctly "incorporate one", a while ago when I designed a built-in wall unit for the livingroom. There was a raciator right smack in the middle of the wall. I built around it, leaving lots of space for access - it's one of those modern, low radiators with the flip-up sheet metal cover, as opposed to a tall cast one. I mulled over the grille for a while, and though I love the look of the old wood covers and thought of ways to make a nice grille, I opted for something a bit different. The local hardware store sells aluminium grilles in 2' x 3' sheets, with a variety of nice looking cutout patterens. I built a wood frame and mounted the grille onto it. With a few squares of strong Velcro, I can now pull the frame off the built-in very easily in order to access the rad for yearly bleeding. As a fringe benefit, the space is wide enough to store a big telescope tripod in, nice and close to the door to the back deck. I lined the top of the cavity with foil-covered bubble wrap because the stereo is directly above the radiator, and lo and behold, even in mid winter, the cabinet holding the stereo isn't even a bit warm.