A rope lock is a construction through which a rope can slip in one direction, but not in the other direction. The rope lock ensures that you cannot free yourself, once you have pulled the rack tight.
A rope lock can be easily made out of metal wire. On the bottom of this page is a drawing and a picture. I made it out of welding wire, but that is not necessary. Every type of metal wire can be used. The metal wire should be 2 mm thick. When the wire is thicker, it is too hard to bend it in the right form. You need two pairs of tongs for constructing the rope lock. You need to put drops of tin or glue at the ends of the metal wire, when the rope lock is finished, because the ends are usually sharp.
Once you have made the rope lock, it has to be inspected very carefully for little damages, caused by the tongs. This can be done by feeling with the fingers, or by looking carefully. The damages can be easily polished away with a screw driver. If you don't remove them, they will damage the rope, and it will become more difficult to pull the rope tight.
