The Thief knot resembles the reef knot except that the free, or working, ends are on opposite sides. It is said that sailors would secure their belongings in a ditty bag using the thief knot, often with the ends hidden. If another sailor went through the bag, the odds were high the thief would tie the bag back using the more common reef knot, revealing the tampering, hence the name. It is difficult to tie by mistake, unlike the granny knot. The thief knot is much less secure than the already insecure reef knot. It unties itself if the lines are pulled when the same action would seize a reef knot.