I saw them in a dreaming while ago. I have even reported that at Ravenfield.
I saw a line that was merging my palm with surrounding glowing yellow-golden light. I was pulled by that line at the other location in dreaming. There I had a significant meeting so, guess pull was with reason.
Lines are energy and are, as Wolf says, a bound with outer Universe. We are connected with all, and lines are everywhere in fact.
The main thing is to get aware of their existence and to get ability to see them.
How to attain this? With allot dreaming, meditation, awareness expanding techniques...and most of all-allot patience

..
It is easiest in dreaming, because there we are not bounded to our physical body and that for we are free from body desires, emotions, pains..., that are grounding us and blocking our vision.
So, in dreaming, when we get aware, we can try to remember to see them.
Castor
''It is a dangerous business, going out of your door. You step into the Road, and if you dont keep your feet, there is no knowing where you might be swept off to.'' J.R.R. Tolkien