There are 2 versions:
1) The raised steeple - when the person is talking, expressing their opinion
2) The lowered steeple - when the person is listening
The steeples should be interpreted in conjunction with other signs. If they are preceeded by positive body language, for example talking with palms open and leaning forward, then the steeple indicates a positive conclusion is likely. If it follows negative signs, for example legs crossed and arms folded, then the outcome is likely to be negative.
This is a confidence/superiority position. The person has their stomach, heart and throat regions exposed which is an unconscious act of fearlessness.
If you are in stressful situation assuming this position can help calm you down and take control of the situation.
Even if someone is agreeing with you, if their arms are crossed they will have a negative attitude towards you.
At this point it is best to attempt to find out what it is that they are not in agreement with you on, or force them out of their stance by asking them to eg write something down.
Their negative attitude will continue until they have uncrossed their arms, once they have done this you will have a better chance of bringing them round to your point of view.
You often see two people talking, standing in the same pose. This indicates that they are in agreement with each other, they like each other. If one uncrosses their arms, the other will do the same. If one stands with one foot forward, the other will assume the same position.
If you want to establish a rapport with someone, mirror their poses - this will have the effect of relaxing them and giving them a non-verbal indication that you are both thinking along the same lines.
The tell-tale signs that someone's feeling uncomfortable or not enjoying the conversation:
The person's head is turned towards you and appears engaged in the conversation - smiling, nodding etc, but their body and feet are pointing away from you.
If someone's body is turned away from you it will be facing the place where they'd rather be. If they're pointed towards another person or the exit then it's time to terminate the conversation or do something to attract their full attention.