Yes I know that there are plenty of other cool knots out there ... many of which I literally couldn't live w/o ... I rock climb. However, this knot is unlike any other. Plus I needed a grabber for my Instructable. :-) (BTW: this ISN'T a climbing knot!) And in truth, it isn't a knot by itself, but rather a system of common knots.
Have you ever tried to tie something down for transporting, but just couldn't get the lines tight and/or during transport the lines would continually loosen? Then this is the knot for you! I learned this knot back in the 70s when specialty car racks and ratchet straps were rare or unheard of. I initially used it to tie a canoe on a car rack, both attaching to the rack as well as the lines to the bow and stern of the canoe. Even with all the new gizmos available today, this knot still shines because all you need is a rope and ropes don't hum in the wind like straps.
The unique aspect of this knot is that it gives you a 2-1 mechanical advantage when tightening the rope. Be careful though. You can actually damage some things because of the mechanical advantage. This knot holds fast and is easy to untie, hallmark traits of any good knot.
Below you see the finished knot system ... we'll break it apart in the steps that follow
Step 1: Initial Setup
The first step is to anchor one end of the rope and then loop the rope around a 2nd anchor point.
For attaching to the 1st anchor point I chose bowline ... a close #2 on my list :-). There are other instructables on that one so I won't bore you here.
The 2nd anchor really should be round because it serves as a pulley in this block and tackle type knot. I've used it on sharp anchor points and it doesn't work as well.
Step 2: Creating a Slip Knot
Tie a slip knot somewhere between the two anchor points. Correct placement of the slip knot takes some experience to judge it correctly. Typically I place it too close to the 2nd anchor point and end up with not enough room to work with. If the knot ends up too far from 2nd anchor point, you can extend the knot by enlarging the loop.
Be sure you tie the slip knot as shown. You may not be able to untie other knots.
In this small example, the slip knot is uncharacteristically close to the 1st anchor point.
Step 3: Tightening and Securing
The loose end of the rope that went around the 2nd anchor point goes through the slip knot loop. Pull the loose end to the desired tension and secure with two half hitches.
Note: To allow better view of the knots, the rope isn't really tightened in this example.
Step 4: Securing Loose End
The final knot is just to secure the loose end somehow. I chose a fisherman's knot to do this.
To tie a fisherman's knot, the rope goes around twice and goes under the "X" created by the loops. Pull the loose end to tighten. Finally slide the knot to put tension on the half hitches.
Step 5: Finished
There you have it. I guarantee that the first time you really use this knot (not just practice), you will be amazed at how well it works and you'll wish you knew this knot a long time ago. You may even come over to my side and declare that is is THE most awesome knot on the planet! :-)
Enjoy and happy hauling,