When I was in Helmsdale last year I met a man, called Jeff, who was rebuilding a wall for some locals. He had been learning how to drystone wall; constructing stones without mortar.

I went out one day to the house with the wall, and had a go. Jeff kept explaining how a tactile relationship with the stones was the most important thing. You could feel the shape and determine if it would slot into the wall.

It was told me to that the best drystone wallers could put a lightbulb in the middle of their structures. They were so skilled that this lightbulb would remain intact with the stones securely wedged around it, without adhesive.

I thought about networks and each actor being mutually relevant to the survival or function of a thing. And I thought about Ceal Floyer wedging lightbulbs into Helix metric rulers. I think about lightbulbs a lot.