The rules for placing gear for anchor stations, whether for lead or toprope situations are no different from those that apply to placing gear on lead, but the consequences of failure are usually more severe. Anchor stations must be bombproof and secure from any directional pull-down, out and up.
How you construct a station depends on the available cracks, the rack you have and the availability of fixed gear. The textbook belay has three or more separate, cam-and-nut-eating cracks, or three large bolts. Real-life anchors are seldom so convenient. Often, your anchor will consist of a bit of everything - a couple of nuts, a cam, and, on popular routes, a fixed pin or bolt - strung across the stance. To a large extent, the nature of the cracks and fixed gear will dictate what you can arrange, but you should still try to set the gear so each piece complements the other. Place a multi-directional cam, for example, to keep anchors, like nuts, from being pulled up and out. String everything together so it is equalized, that is, each piece bears an equal load.
The horizontal distance between each of your anchor placements and the length of the slings you use to connect them are as important, if not more so, than the method you use to equalize the anchors. This is because as you spread anchors apart horizontally, they pull sharply against one another, lever style, multiplying the force instead of reducing it. The farther apart the anchors, the greater the potential load multiplication.
In any belay- or rappel-anchor situation, arrange the anchors so the angle formed by the slings at the master-connection point is less than 60 degrees. At this angle, the load on each equalized anchor is 58 percent. Increase that angle to 90 degrees, and the load on each anchor increases to 70 percent. Go up to 150 degrees, a realistic scenario when connecting anchors with short slings, and the load on each anchor can reach 200 percent!
The good news is that you can use slings to extend the anchors, keeping the angle formed between the slings at 60 degrees or less.
You have two kidneys for a reason: The organ is mission critical. If you only had one kidney and it conked out, the mission - your life - would end. Redundant systems keep the game going even when one component fails. Belays are mission critical: Double up all key components. Even the best equalized anchor is junk if you clip to the master point with just one carabiner, and that carabiner breaks (it has happened). Use two carabiners, ideally locking ones, to connect yourself to the master point. Likewise, double up all critical slings, and compound your anchor by placing three (or more) cams or nuts instead of two, and backing up fixed gear, pins and old bolts.
When you take a sling, give it a half-twist and clip through the twist you create the Sliding X, a common, simple and highly effective equalization method for two anchors that has the additional benefit of being the only system that readjusts itself when the angle of loading changes. Nevertheless, it is not recommended. The single sling is not redundant, and if either anchor point fails, the remaining piece is subject to a shock-load of up to two tons, depending on the distance between the two anchors.
Improved Sliding X
Tie an overhand loop in both sides of the sling or cord above the X , and you dramatically decrease the shock-load potential. The trade off: The closer you tie the overhand knots to the X, the more you reduce the system`s ability to equalize. Despite this limitation, the Improved X is good alternative when you are low on slings. It is also a good method for equalizing pro on lead, and equalizing two anchors that are in turn woven into a cordelette-rigged belay.
Piecing together an anchor by using a sundry of slings remains popular, and when used properly, sling anchors can equalize. The system is also redundant, works with an infinite number of anchors, and has a low risk of shock-loading.
For slings to equalize, their lengths must be precisely adjusted by adding slings to lengthen or tying overhand knots to shorten them. With all this guesswork and fiddling, you`ll seldom end up with a truly equalized anchor. One sling is nearly always a bit longer than the other, causing uneven loading. Even when you do get the anchor adjusted just right, the load is only equalized when it pulls straight down on the power point. If the load pulls off to either side, it will not be equalized. A final consideration is the fact that perlon and slings all stretch differently, resulting in potentially unequal anchor loading.
For simplicity, redundancy, ease of use and low-potential shock loading, the cordelette is the gold standard for equalizing anchors. Use a dedicated 9-foot loop of 7 or 8mm perlon (some companies make perlon just for cordelettes; other manufacturers offer cordelettes pre-made from webbing); clip each anchor into the loop, pull down the length of cordelette between each anchor, gather these to an equalized point, and tie them together with a figure-eight loop. The resulting loops formed by the figure-eight become the power-point. The crux to properly setting a cordelette is guessing the direction the anchor will be loaded. For instance, if you know the anchor will be loaded off to the left, tie the cordelette so the power point is off to the left. Since a cordelette only equalizes in one direction, you need to get this right. Guess wrong, and just one piece will bear the brunt of the load.
Properly rigged, the cordelette will equalize the anchors; should one point fail, shock-loading will be minimal. To further protect against an unanticipated off-center loading, place a directional anchor such as an upside-down slotted nut and clip this to the power-point loop.
When you arrive at a belay and don`t have a single sling or cordelette to construct your anchor, you can simply use your rope and the Double Figure-Eight to equalize two anchors. Although the knot is difficult to adjust such that the two anchors share the load exactly, the Double Figure-Eight, when you get it right, works well, and has a low shock-load risk. It does, however, eat up rope, especially when your anchors are spread far apart, and only works for two-point anchors. When you have three pieces in, and assuming you have a sling, you can clip the third anchor to one of the Double Figure-Eight`s loops, adjusting the sling to the appropriate equalized length.