A Crossing is a planar seam shallow enough to permit direct passage from one stable reality to another. The traveler does not need to navigate an extended journey through The Verge because the transition between the two realities has become sufficiently compressed to be experienced as an immediate threshold.
A Crossing may appear as a doorway, cave opening, arch, mountain pass, ford, stretch of open water, or almost any other boundary through which passage can occur. The apparent form is less important than the metaphysical relationship involved: crossing the threshold carries the traveler from the stable conditions of one reality directly into those of another.
Crossings may be permanent, temporary, or recurring. Some remain continuously accessible, while others open only when physical, magical, astronomical, emotional, divine, or historical circumstances strengthen the underlying planar relationship. A Crossing may therefore be familiar and predictable without being continuously available.
The Verge is still involved in such travel; it has simply become too shallow or brief to require a journey. Planar travelers summarize the practical distinction with a common saying: a Crossing is a door; a Vergeway is a road.