A leyline is a great big line, of energy, connected to a network, of the world. That makes it able, to influence people. As, all that's needed be a group, of people, to cause the influence, otherwise, its an energetic moment creator. It has capacity, of energy interaction, to cause a person, to burn out, temporarily. So yes, it holds enough Energy, to act as a gateway, as well. Thats the simple terms, of what a leyline be.
But then going into specifics, again its part, of the network, of the world, so to speak, if one is near you, then its the spoken intention, that causes the influence. But, only if you had a strong enough will. So, reprograming, fixing, changing directional flow, be easier. The leyline has a tendency, to make people's works come true, but its all part, of a net program, from the earth so reprograming and changing flow is a bit harder than direct intent. You have to factor in the network, as a whole.
So yea, you got to direct your intent, at the leyline, and not just a specific point. The network, of the earth, uses these leylines and you can program one point, though its programming most the network. A simple way to cause it to effect one area be to focus your mind on that area, to effect it by stating your intention at the leyline, and think, 'it only effects the area I thought on.' As a group, this works easier, than if you have a very strong will worker.
So, there be almost a sentient life, in the network and it tends, to get info and feed off certain sectional points, of highly concentrated energy and if the specific area, in which you are tapping into has a strong influence, on that particular leyline, this makes it hard to change. Which is why, it takes a group, or a very strong will worker. But, if your not used, to it your gonna get a jolt, you could fry your system for a bit.
You can treat powerlines, as though they were a leyline. If one be near you, then it can be used. In which, the nations energy grid, be the powerlines network. That you can tap into. But, beware power outages, that could occur.