U nlike flying or astral projection, walking through walls is a totally earth-related craft, but a lot more interesting than pot making or driftwood lamps. I got started at a picnic up in Bowstring in the northern part of the state. A fellow walked through a brick wall right there in the park.
Stone walls are best, then brick and wood.
Wooden walls with fiberglass insulation and steel doors aren't so good. They won't hurt you. If your wall walking is done properly, both you and the wall are left intact. It is just that they aren't pleasant somehow. The worst things are wire fences, maybe it's the molecular structure of the alloy or just the amount of give in a fence, I don't know, but I've torn my jacket and lost my hat in a lot of fences.