Anchors provide the foundation for rope rescue. They can be man-made (e.g., bolts, eyes, vehicles, etc), natural (e.g., rocks, trees, etc), or a combination of the two (e.g., climbing cams, pitons, ice screws, etc). Anchors can be tied around a single object ("single-point") or by joining multiple anchors (i.e., "multi-point").
This page explores key considerations when selecting anchors. The next page shows examples of several types of anchors.
Three acronyms, ERNEST, SERENE and SAFE, are used to identify important considerations when selecting an anchor.
Equalized
Redundant
No...
Extension
Strong (Solid)
Timely
Strong (Solid)
Equalized
Redundant
Efficient
No...
Extension
Strength
Alignment
Focal Point
Equalized
The concepts in these acronyms are very similar. Anchors should be strong enough to have a sufficient safety factor. The forces should be equalized between the various ropes and anchors. Many protocols require that all rigging elements are redundant so they can pass the "scissors test." Anchors should be designed so they won't extend if a portion of the anchor fails (which would result in a dynamic shock load). And you should be able to build the anchor in a reasonable amount of time.
The "critical point test" (aka "scissors test") requires that if any one item fails, nobody should be injured.
A "bend" is a knot that joins two ropes.
A "hitch" is a type of knot that must be tied around another object.
The "whistle test" requires that if all rescuers let go, nobody should be injured.