Trespassing allows you to manipulate the objects of another player, such as to light their fires or use their structures, and also to open and look inside containers. Be cautious, since each time you perform such an action, you will leave Odor of Trespassing scents, which can be harvested by anyone with Ranging and sufficient exploration/perception. This could get you into trouble, and even killed, since this scent can be used to locate you or your hearth fire.