3 Piece Quad Anchor

The quad anchor is favored by many for its simplicity, strength, redundancy, and perhaps most importantly, self-equalization. It’s traditionally used on bolted belay stations since it requires two points of attachment. However, if there is no bolted anchor you can still use a version of the quad that clips into three pieces of protection.

The side with one piece gets 50% load

The three piece quad is asymmetrical – above one of the limiter knots it clips into a single piece of gear, and above the other clips into two. This means that the load will not be equally distributed between all three pieces of the anchor. Each side of the anchor will take 50% of the load, so the side that clips to a single piece puts the full 50% on that piece, while the side with two pieces distributes 25% to each piece (except when it doesn’t – more on that later).

Since one piece of the anchor is always going to get 50% of the load, that piece needs to be bomber, and typically you’d have your best piece be the one that is clipped alone. That means that if your pro is placed laterally, you’ll need the strong piece to be on either the left or right, or else you won’t be able to clip it by itself.

The other side may also load either piece at 50%

Remember when I said that the side with two pieces of pro doesn’t always distribute the load evenly between those pieces? As the direction of pull changes, the anchor will self equalize, but only partially. As the load moves to the left, only the rightmost of these two pieces will receive the load. And as it moves to the right, only the left piece will receive it. This means that only when the load is straight down (or in whatever direction the anchor was pre-equalized in when the limiter knots were tied) will the load be distributed evenly among the two pieces (50/25/25). The rest of the time the load will be either 50/0/50 or 50/50/0!

When the direction of pull comes from the left, the leftmost piece of gear is unweighted. When the direction of pull is from the right, the middle piece of gear is unweighted.

This distribution is better than 100/0/0, which is what happens with “standard” pre-equalized 3 piece anchors when the direction of pull changes (or if the anchor was equalized in the wrong direction), but may not be what you would assume. This means you should only build this anchor off of three good pieces, where you’d be ok with any one of them holding 50% of the force by itself.

Strengths and weaknesses of the 3 piece quad

Pros: Self equalization much better than standard 3 piece anchor; may be easier to build than other self equalizing anchors that require 3 or more pieces of gear.

Cons: Redundancy isn’t the best since the load is often on just two pieces. Because of this, requires three solid gear placements.

When to use a 3 piece quad

The 3 piece quad is a good choice for when the direction of pull on the anchor will change, and when 3 solid placements are available. In multipitch climbing, usually we know that the direction of pull won’t change much. When belaying the follower, the direction of pull is the line between the master point and the last piece of protection, with a few caveats (Could the last piece of gear pull out? Is there a traversing runout between the last piece and the anchor? Is the last piece of pro extended very significantly?). When belaying the leader, the direction of pull only matters if the leader clipped the anchor, and in that case the direction will either be straight down (a factor two fall) or the line between the anchor and first piece of gear.

Since we can usually predict the direction of pull in a multipitch climb, equalizing three pieces of gear in a single direction is usually good enough. But I would consider a three piece quad if I weren’t confident that I could equalize the anchor in the correct direction, since a failure to do so could result in a 100/0/0 load scenario.

The 3 piece quad makes more sense as a toprope anchor where there is no bolted belay and the climb traverses.

Fixing the 50/50/0 problem

If you find yourself in a scenario where you need a self equalizing anchor but don’t feel wonderful about all three placements, you won’t want to build a 3 piece quad as there may be one or two pieces that you don’t want to receive half the load. To work around this, equalize the less optimal piece with another piece with a sliding X, then build a normal quad between the remaining piece and the master point of the sliding X.