An acronym to determine if an anchor is ideal. Let's go over what each letter means.
The weight is equally distributed on each strand of webbing when weighted by the rappeller.
For example, if you have two loops of webbing connected to a pair of bolts or around a large tree then each loop should hold about 50% of the weight. If there are three loops of webbing around three anchors each should hold about a third of the weight.
The angle between any two strands of webbing should be at most 90° (right angle). More than that produces a significant amount of force on the anchors. Here's a simple list of the angle between the widest two strands and how much force is applied. The assumption is that the two anchors and their master point create an Isosceles triangle.
Redundancy in an anchor means that if one piece of the system fails, the entire system will not fail. In canyoneering this would mean that if a piece of webbing gets cut through on a rock or if a bolt pulls out then the rappeller will not fall.
This is the "N" and the "O". No extension means that if one of the anchors were to fail then the rappeller wouldn't fall any distance and the surviving anchor would not be shock loaded.
A very small amount of extension (like an inch or two) is often considered acceptable if it means better equalization. Examples of anchor rigging that has almost no extension are the equalette, quad, and redundant wrap.
Solid simply means the anchor can easily sustain typical forces from rappelling and even shock loading without the possibility of failure.
Sometimes I hear the word "Strong" in place of "Solid". They mean the same thing.
Timely means the anchor is evaluated and rigged in a timely manner. If it takes a long time to do this then it is inefficient, boring for the others, and they can lose confidence in the rigger's ability to rig.