When dealing with block and tackle systems if the terminal end (the knotted portion) of the rope is attached to the load the system will have an odd number. If the terminal end of the rope is attached to the anchor, the system will be an even number. As I stated earlier, figuring out the mechanical advantage of a system is a visual skill. Food for thought, if you don't have rope equipment to train on grab a pen and paper and draw some systems yourself. It's a simple way to stay sharp on a important skill.
Let's now talk about the foundation of any rope system, the anchor system. Anchors are the foundation of any rope system and your system is only as strong as your anchor. For this reason, great care should be given when choosing your anchor.
There are two categories of anchors, bombproof and pseudo. Bombproof anchors are considered to be structural members. To simplify it further think of it like this. if the structural member fails it would have a catastrophic effect on the structure itself. That's an easy way to decipher if your anchor is bombproof or not. Pseudo anchors are simply any anchors that are not bombproof. There is one rule pertaining to psuedo anchors; they must be backed up by an anchor of equal or greater strength and size.
On a safety note, get in the habit of backing up all your anchors. Doing this will only broaden your safety margins.
When constructing your anchor system always consider the direction of pull. Basically what this means is when your main line is loaded it's going to find its plumb point. Your job is to anticipate that point and keep your anchor in line with it. Granted this can not always be done. However this is not a problem. We can use something called a directional pulley. Basically a directional pulley is a means to redirect the rope in a more desired position. If we don't have an anchor in line with our main line's plumb point we can use a directional pulley to bring it to that location. Remember the anchor that your directional pulley is on should be bombproof because it will see a greater load than the main anchor is seeing.
Vehicles, preferably large ones, can be used as an anchor. However, you must chock all four tires, put the emergency break on and take the keys out of the car. When anchoring to a vehicle be sure to anchor to a structural component such as the frame.
One last anchor type to talk about is artificial anchors. Artificial anchors are special types of hardware designed for the purpose of being an anchor attachment point. This type of anchor, which includes bolts and cams, is mainly used in sport climbing. However, heavy duty steel anchor plates that can be bolted down are used in urban rope rescue.
Edge protection is essential in most any anchor system. Take the time to inspect the object or objects you're utilizing for your system. Look for abrasion points or areas that will cause damage to the rope, webbing or anchor straps in your system. These areas can be simply padded out using manufactured edge protection, by placing an empty rope bag or an old section of hose over the area (see Figure 7.)
Remember when in doubt, back it up.
The third component to our mechanical advantage system is a belay system. The belay will catch the load in the event of a main line failure or any other reason causing the main line to release. Your belay should be what's called an automatic belay. What that means is the belay will activate on its own, eliminating any potential human error. Your belay system should be assigned its own separate anchor attachment point. What that means is on a bombproof anchor the belay should be connected to a separate anchor strap than that of which the main line is attached to. When dealing with questionable anchors an entirely separate anchor should be utilized to ensure safety.
A sub-category belays can be put in would be "hard" and "soft" belays. Hard belays meaning the belay is a piece of hardware such as a 540 Rescue Belay. The term soft belay would refer to a pair of tandem prusiks. Don't confuse a progress capture device (PCD) for a belay. They may look the same. However, their jobs are very different. Belay and anchor systems will be looked at more in-depth in future articles.