|The symbolic role of the Edge|
If, as we have seen, the carpet's internal part must be considered as an image of the Divine, of the spiritual and timeless world then it's logic to understand the rectangular border as a figurative representation of human dimension and real time.
This idea is graphically suggested by repetitive patters that usually adorn the carpets' frames, with their rhythmically recurring patterns remembering us of the Time and its passing. Therefore it's possibile that the succession of light and dark motifs, which is common in several carpets, stands for the Day and Night cycle.
Eastern carpets often represent the flowing of Time with a recurrent metaphor: the infinite shoot which flowers and leaves regularly born from. It was often so stylized that it became impossible to read leaving just a bunch of flowers and leaves spreading in alternate directions. In chinese carpets we often found a swastika motif, ancient solar symbol, which represent the infinite temporal flowing of time.
The edge referred to the time is in contrast with the a-temporality of the entire field symbolizing the paradise creating a combination within finite and infinite, temporal and spiritual, and evocating a model of the Universe seen in the majority of Asian cultures as a heaven beyond the sky and separated from Earth by a legendary Celestial Portal.
Since the carpet's border was meant as a frame by which it was possible to see Heaven, it was logical to understand it as a Celestial Portal. Like the carpet symbolically marked the transiction point between human world and spiritual world so the border was the point between the spiritual world ( or a terrestrial reflection of this ) and the human world, namely the house or the tent surrounding them.