How to Tie the Thief Knot
The Thief Knot is not really what I would call a practical knot, in that it can assist in a particular task strength/weight related task. It was as I understand it a form of sack knot, but rather than just keeping a sack closed, it would indicate if a sack had been tampered with!
ABoK 1207 “The Thief or Bag Knot is also called Bread Bag Knot. It appears very like the Reef Knot, but there is one real and scarcely evident difference. It does not consist of two Half Knots. There is a legend that sailors tie clothes bags, and bread bags with this knot and that thieves always retie them with Reef Knots and so are inevitably detected. It is a pleasing story that should encourage honesty.
Here is a short video on how to tie the Thief Knot and it also shows a comparison to the Reef or Square knot. Thief knot and the Reef knot are similar, however on a working ends on a thief knot exit the knot on opposite sides. Whilst on a Reef knot the working ends exit on the same side.