Problem/Background: When I first started diving into canyoneering-specific rigging methods, I became intrigued with contingency anchors. They are advertised as a solution to several problems that teams can encounter in canyons, and at face value, they seemed rather ingenious. "Rigging for rescue" was heavily promoted in some of the material I was learning from. I experimented with several common methods I found online and became a bit puzzled. Some common methods didn't seem to work at all. Others worked in certain circumstances, but could easily be accidentally released. With further research, I found several instances where releasable rigging was involved in accidents and deaths. At this point, my initial reaction was to completely dismiss them as unnecessary complexity for almost all circumstances - with the exception being "real" class C canyons. I still found them rather amusing, and I was curious why people used them regardless of their documented issues. I learned more about rope work, experimented with many different blocks, and I eventually came to the following conclusions (for myself): Riggings that rely entirely on non-locking friction are unreliable. Ropes and components wear in and conditions change. What worked once may not work the next time. An unexpected lack of friction in this type of rigging has been implicated in at least one accident. Riggings that rely on a lock created by two non-fixed components are unreliable. Many "blocks" do not have a fixed lock as a part of their design, but rely on the lock provided by the rope being pinched between the anchor and the "block" device (demonstration of some non-locking configuration, another "block" that relies on the interaction with the anchor). External factors such as movement and rock geometry can cause this lock to release under load. If this is the only locking mechanism in the system, it becomes dependent on friction alone to hold the load, which is unreliable per #1. This scenario likely contributed to at least one fatality. Releasable rigging should be easily releasable. For a contingency rigging to provide value, it must be easy to release into a lower. Some common riggings (including the "standard" locking figure 8 block) address #1 and #2 but are not easily releasable (example). In the case of the standard figure 8 block, this happens because the strand that you need to loosen in order to release to lower is locked by a strand that is under load when the system is weighted. This has been an issue in at least one incident. Riggings should be easy to inspect. Visual complexity is difficult to verify, and the human eye is good at spotting symmetry. This is why a figure 8 knot is easy to inspect. Un-inspected riggings have been involved in accidents. Riggings should not depend on specific hardware. (a bit of personal opinion) Being dependent on a single piece of hardware is a liability, since it could be forgotten or lost. Ideal riggings should be able to be constructed with materials commonly on hand in canyons, which includes carabiners, rope, slings, and figure 8-style rappel devices. Possible Solution: The below is a block that can be constructed with figure 8 style devices that I have not yet seen elsewhere. I came across this after being disappointed that most existing designs I could find not meeting the above criteria. It is based on the Secure Compact figure 8 block, but it adds a locking half twist in the last bight. This locking twist occurs entirely on the non-load bearing side of the lock created between the block and the anchor, so it is trivial to release under load. I find this variation very easy to inspect because it has a symmetric appearance (although it isn't truly symmetric). It is also easy to inspect the critical piece (the lock) by asking the following: Does the rope form an obvious "X" on top pinching the exit strand? This also can be constructed with most any figure 8 style device you may have on hand and is not particularly dependent on features of a single device. (I find the Euro 8 rather slick, but it requires a "classic" figure 8 device, where the small hole is large enough for a bite of rope to fit through). This style works with common rope sizes, tested with 8-11mm. With 8mm and 11mm rope, resepctively: With various figure 8 style devices (probably works with other common devices, but unverified): Notes: I generally would prefer a MMO which also meets all of my criteria, but there are some benefits of using a device (smoother, less rope twist, less rope-on-rope friction, does not require re-rigging for LAPAR) I would still always secure the bag side of this (or any) releasable block, unless the tail is being actively managed by someone at the anchor I wanted to share this because I was rather disturbed with the number of accidents involving contingency anchors. It is possible that this or other solutions are well known in the "real world", but the readily searchable information I could find online left a lot to be desired.