It’s a long way down, but the Sears Tower hopes that a new attraction will boost tourism. Today, the Sears Tower opened four glass enclosures, called the Ledge, on the Skydeck’s West side. The Ledge enclosures will extend more than four feet beyond the building, and will be retractable so they won’t interfere with window washers. Similar glass-floored views at the Grand Canyon and the CN Tower inspired the Ledge. The Skydeck hopes the new attraction will draw more visitors, particularly locals who may have given up on going to the top of the Sears Tower. But not those with even the slightest fear of heights. The glass will be three layers thick and each layer will be a half-inch thick. The balconies will be able to hold about five tons. The Ledge will be part of regular Skydeck admission, which went up to $14.95 Friday. If you want to experience the Sears Tower’s Ledge, try to get it in before the building is renamed to the Willis Tower later this summer.