The Leave No Trace principle, or LNT, is a set of rules and guidelines implemented at Philmont in order to maintain the natural aspect of the ranch. The most commonly referenced part of LNT is "Take nothing but pictures, leave nothing but footprints". This is to stress not to leave any sign to later campers that you have been at the area, such as graffiti or litter, as well as not to take anything from the area, such as archaeological artifacts or natural things such as plants or rocks. LNT is greatly stressed at Philmont, though not so much in some areas where it is impractical to completely follow, such as fire rings and horseriding based camps. One easily identifiable aspect of LNT is the implementation of sumps in the backcountry, which are used so as to prevent rampant littering of cooking and cleaning waste. Also used are bear bag lines, which are a better alternative to bear boxes, as they do not mar the landscape as much. There are several LNT courses available to scouts, and some are taught at the Philmont Training Center.