I’ve done some research on portals/gateways, and based on my findings…wouldn’t an altar or a sigil be considered a portal?
If a sigil is opened then it’s like a line of communication and a “gateway” for that spirits energy. An altar would seem like a portal/gateway as even with the small altar setup I have, I can definitely notice an energy/vibe at the altar, and in turn my room (where the altar is located) feels different.
An altar becomes a nexion for the powers it is consecrated to. An open seal is the same. That is why in Works of Darkness, EA Koetting recommends beginners not have more than three seals open at the same time lest the Powers run amok.
or if you meant that rope around the altar space in my opinion you dont even need that the enities decide the square area of the sacred space during your rituals