anchor point: an assigned or agreed-upon point of boundary, which is conceived to be motionless by the individual; one of the points which demarcate the outermost boundaries of a space or its corners for an individual. —PDC 2 Approved Glossary
anchor points: dimension points which demarcate (limit) the outermost boundaries of a space or its corners. Anchor points, along with the viewpoint, are responsible for space. An anchor point is a dimension point that stays rather still, to keep the space created. See also dimension point in this glossary.—Individuation Approved 26.2.91
Consider that all the content of physical space is continually melting out of existence. To get a feel for this, recall what space looked like for Frodo when he donned the One Ring. Matter melted from objects at their boundaries and wafted away like steam. If positions depended on surfaces or substances there could be no persisting positions over time. Any real (x, y, z) would have only a momentary existence. Only an ideal (x, y, z) can persist over time.
An anchor point is a persisting point-position, and it is persistent because it is ideal—it is projected by the perceiver. Imagine projecting the cross-hairs of a rifle scope on a wall. The center of the cross-hairs specifies a position on the screen, a stable point. But the stable point that is picked out does not subsist in the substance of the wall. We could not mark the point with a Sharpie but only the underlying substance (which is melting away).
What, then, is the origin of our sense that space is permanent? Permanent space can only be ideal—a set of positions that I project. The stable point does not exist on a substance, but only in projection.
An anchor point is not a topological subspace of a physical surface, which melts away, but a position posited in projected “space.” I project x, y, and z axes in my imagination across real space. Right now I cognize a point in my room. This point is ideal. And it is only my imaginary space that is permanent. Stable positions can only be projected from a static.