A device used to determine geographic direction, with a needle that points to Magnetic North (see magnetic declination). An orienteering compass with a movable dial (see photo) is the minimum requirement for letterboxing, but sighting and lensatic compasses can be more useful in pinpointing specific degree coordinates. Electronic compasses are also available, but are more sensitive to external magnetic interference. Your compass will get a good workout, so invest in a high-quality, durable compass, avoiding cheap compasses without liquid-filled dial (these rarely provide accurate readings). To find a certain bearing, turn the dial of a compass until your desired degree is aligned with the direction-of-travel arrow pointing ahead, and turn the entire compass until the needle matches the orienting arrow underneath. Find a landmark and follow the direction-of-travel arrow to it, and repeat.