When you speak of the North and South poles, do you mean the directions, and which length should be longer?
Yes, they are the directions. The length of a place in the North-South direction should be longer than its East-West length; such a place is considered the best because it holds the strongest magnetic field.
Related questions
Can a mirror be fitted on a wardrobe in the S, SSW, SW, WSW or West?
No. Wardrobe mirrors also belong on the North or East wall. Some say the North-West is also allowed because the mirror represents the water element and the Moon.
Can a nandavart dwar be made in a flat?
Yes, it can be made in a flat too.
If a house has four members, whose kundli should be used for its vastu?
Primarily the grih swami's, the person whose money is going into the house, because the house affects the owner and his next three generations; do not go by the name the property is registered in, such as a daughter. The facing and main door are chosen from the grih swami's chart, for example North if his Mercury is exalted or his North-side planets are strong. Where a child sleeps or studies is decided from the child's own chart: if the child's Mercury is weak, seat him in the South instead of the North, following the 180-degree rule for a weak planet.
If the dressing room is in the SSW, can a mirror not be used there?
A dressing room has four walls, so fix the mirror on its North or East wall. If the wash basin is already in the South and its mirror must be there, fix a mirror of the same size on the North wall; the pit made in the South is matched by one opposite and the effect evens out.
Must the house be at 0 degrees for a sarvatobhadra dwar?
By definition it is at 0 degrees with doors in all four directions, but it can be made otherwise too: build the doors on whichever pads fall on Pushpdant, Grihakshat, Bhallat and E4.
The kundli chart was shown with directions. How are those directions used, and what can a kundli tell about a house?
Go by the houses, not the numbers written in them: the top house is the 1st house (East) and the 4th house is North. If the planets on the North side are strong, the North direction is very good for the person. A kundli can even reveal where a person's house is, where its door is, how many windows it has and where a nearby river, pond or temple lies, so a map of the house can be drawn without seeing it.