Here's the math. Two anchor legs on each side rated at 4,000 pounds each = 8,000 pounds. 8,000 pounds x 2 = 16,000 pounds. If you look at the picture, you'll notice the water knot is located on the back of the anchor and not part of the two wraps we've pulled. That's because the knot is the weakest point in this system.
By positioning it where we did the wraps in the system absorb most of the friction that the knot would have seen. On a side note, remember always leave about two inches of tail on either side of your water knot for safeties (see Figure 4.)
Another basic anchoring method is called a load sharing anchor system and it does just that. This is created by using two separate anchor points which in essence will become one. In Figure 5, you can see this anchor system created by using two pieces of one-inch webbing. Our degree of angles really comes into play now.
Remember as we said earlier, we want to keep the angles we create in the area of 45 to90 degrees. The angle we have in Figure 5 is 45 degrees. So if our load was one thousand pounds, each side of the anchor system will see approximately 500 pounds. Load sharing anchor systems are great when your load force is directed downward in a straight line.
How about if there is the possibility of your load moving from side to side? Simple solution, it's called a load distributing anchor system. This is a system comprised of two or more anchor points designed to move with the load. In other words, if your load moves to the right the anchor system would equalize the load amongst all the anchor points.
If you look at Figure 6 you will see an example of a two point load distributing anchor system. It's utilizing two anchors just like a load sharing anchor system however by rigging or building it differently we can achieve a different type of anchor system that will equally distribute the load amongst itself as opposed to only sharing the load equally in a vertically plumb direction .
A good habit to get into is backing up all your anchors. In Figure 7 you can see an example of this. Some may say this is overkill when using bombproof anchors; however if you have the gear it will take all of a minute to further ensure your safety. In Figure 7 we simply tied a directional eight (a form of the Figure 8 Bight knot that can be tied to face left or right), wrapped the anchor with a piece of one inch webbing and made our connection. All of this is done in under one minute. An extra minute in your rigging is worth the extra safety it provides, if you were to ask my opinion.
Knowing how to construct these anchor systems is only three quarters of the skill set you should have. There are circumstances where your anchor points won't line up with the ropes needed location. This is not a big deal. We can use what's called a directional pulley, or "directional." A directional pulley is rigged to a separate anchor point and if need be, extended to a desired length to direct the rope in its needed position. Ideally the anchor point chosen for this should be considered bombproof. If it's not it must be backed up with an anchor point of equal or greater strength. You can see an example of this in Figure 8.
The foundation of all the skills we've talked about in this article will stem back to how to choose an anchor and what characteristics to look for. We talked about bombproof and questionable anchors and the difference not only between them but how our rigging will differ. We should also be looking for abrasion points, or rough and/or sharp areas of that anchor object that will damage the rope. If you do find trouble spots simply pad these areas out with rope pads, rope bags, or whatever will do the trick. Once the system is loaded, monitor these areas to ensure the rope hasn't moved off of the protection in place. It's also a good idea to find an anchor that is in-line with the desired rope destination. By doing this you can avoid using a directional pulley.
Keep the big picture in mind and avoid getting tunnel vision. Here is an example for you. If I brought you to a bombproof anchor and told you I needed four separate anchor attachments using one length of rope to create them, how would you do it? The answer is shown in Figure 9. Every time you tie a Figure 8 Bight in the rope in essence your now working with a new length of rope. So by doing this I can achieve multiple anchor attachment points that are isolated from each other utilizing only one length of rope.