In Exodus 25:11, this signifies the fixing of bounds to good to avoid harm from hellish evils. (Arcana Coelestia 9492)

634. It is extremely difficult however to state intelligibly what the understanding of truth and the will for good are, properly speaking. The reason is that everything man thinks he ascribes to the understanding because he calls it so, and everything he desires he ascribes to the will because he calls it so. And it is even more difficult to state what they are in an intelligible way because the majority nowadays are also unaware that what belongs to the understanding is distinct and separate from what belongs to the will; for when they think something they say that they will it, and when they will something they say that they think it. Their speaking in this way is thus one reason for the difficulty. And a further reason why it is difficult to grasp the matter is that such people are engrossed solely in bodily interests, that is, their life consists in things of a more external nature.

[2] For these same reasons people are also unaware of the fact that with everybody there exists something interior, something more interior still, and indeed something inmost, and that the bodily and sensory part of a person is the most external. Desires and things of the memory are interior, affections and rational concepts more interior still, while the will for good and the understanding of truth are the inmost. Nothing could possibly be more distinct and separate than these are from one another, yet a bodily-minded man sees no difference at all, and so confuses them all with one another. This is the reason why he believes that when his physical body dies, everything else will die as well, when in reality only at that point does he start to live, and to do so indeed through his own interior things which are arranged in consecutive order. Unless man's interior things were distinct and separate in this way and arranged consecutively, men could not possibly be spirits, angelic spirits, or angels in the next life, all of whom differ in this way from one another according to things that are interior. Consequently the three heavens are very distinct and separate from one another. From all these considerations it now becomes clear to some extent what the understanding of truth and the will for good are, properly speaking, and that they are attributable only to the celestial man, or angels of the third heaven.