Before any building starts, the gap has to be taken down. This seems backward at first. Part of the wall has fallen; surely the thing to do is to put it back up. But the stones on either side of a gap are usually loose too, leaning or bellied out where the wall began to fail, and new work built against loose work will not last. So the waller takes the wall down on each side until reaching stones that are sound, firm in their places and not moving when pressed.
The ends of the gap are not taken down straight. They are stepped back, like a staircase, with each course a little shorter than the one beneath it. This means that when the new work is built, it can be knitted into the old, with new stones lapping over old ones at each step, instead of meeting them along one vertical seam, which would be a weakness running all the way up.
As the stones come off, they are laid out on the ground in an order that will make sense later. They go on both sides of the wall, because the wall has two faces and each will be built from its own side. They are placed a little way back, far enough to leave room to stand and work, but close enough that nothing has to be carried far. The biggest stones go nearest the wall’s foot, since they will be needed first. The flat, wide, even stones that came off the very top are put to one side, well out of the way, because they are the last thing to go back on and must not be buried under everything else.
Then there is the small stuff. Every dry-stone wall has two faces of larger stones with a core of smaller ones between them. This core is called the hearting. When a wall comes down, the hearting comes down with it, a heap of fist-sized and smaller pieces that looks like rubble. It is not rubble. It is as important as anything else in the wall, and it is gathered up carefully and kept in its own pile, sometimes in a bucket or two, so that none of it is lost in the grass.
A waller who has done this for a long time can tell a great deal from the way a wall has fallen. Usually the cause is water. Frost gets into the joints and lifts them a little, then thaws, then freezes again, and over a few winters the stones work loose. Sometimes the foundation has sunk at one point because the ground was softer there. Sometimes a tree root has pushed up underneath, or a sheep has rubbed against the same spot for years. On the hill wall it is mostly frost, and the small spring that comes out of the slope about a third of the way up and runs under the wall’s foot in wet weather.
By the end of the first day, the gap is wider than it was, and there is a long double row of stone laid out on the grass on either side, with the hearting in its heaps and the top stones set apart. It looks like more of a mess than when the work began. It is not, though. Everything is now where it can be seen, and the wall can go back up in the right order.