a) A node is found at the intersection of two or more energy lines, particularly serpent lines/ dragon currents, giving a highly charged point of energy, often associated with a power centre. Usually the lines will narrow to a point at the node.
b) Seven nodes are to be found on most ancient standing stones. Five are above ground level and two are on the section of the stone below ground level. They are likened to the seven major chakras of the human body. Nodes can be found at many places other than standing stones.
(Source: British Dowsing, britishdowsing.net)