It's hard to believe a massive rock wall could have any heart in it, but that's exactly what binds a dry stone wall together, says English-born rock expert John Shaw-Rimmington -- and he isn't speaking metaphorically.

"The rock chips, pebbles and fragments that are packed into the spaces between larger stones are called 'hearting' and they're what hold a wall up," he explains.

In most cases it's invisible, but a wall with plenty of heart in the right places will last 100 years with little or no maintenance, says the Canadian rock star, who is president of the Dry Stone Wall Association and is leading a revival of the ancient art form. He visited Victoria recently to instruct more than 30 students who built two walls measuring about 1 1/2 metres high by 20 metres long over the course of six days.

"[It's] a mental challenge more than a physical one," said one student who helped build a wall, which includes layers of horizontal stone topped by vertical pieces stacked like books.

The Ontario teacher says the work is not back-breaking, but it is labour-intensive.

Jackie Hiebert, who attended the course with her 75-year-old father, says it was a "good tired."

"It's very addicting, a mental challenge more than a physical one, really. You look for the right size rock, the right face, and then see how it knits together. It's exciting to make things from what's just lying around. In England, farmers pick up rocks and make walls, whereas here we blast it and take it away," says Hiebert.

Shaw-Rimmington says he can teach anyone the basics in just two days, but that it takes a lifetime to master the art. "A person just has to love the material, and be able to think like a stone," he jokes.

He worked as a stonemason for 25 years before learning the ancient dry-wall techniques. He specialized in restoring old pubs, repairing old houses, barns and Scottish-style stone churches, using wet bonding materials and cements.

"I loved making something that looks old and has a sense of history," he says. But he gradually tired of doing work that was basically just veneer. "I realized it was a bit cheeky to ask stone to be glued to the side of a building rather than a structural part of it. And thus began my quest 12 years ago to use stone structurally."

He believes people carry a genetic history of good stone-walling -- "It fell by the wayside after innovations such as Portland cement" -- and decided to get in touch with his inner dry-waller. A final insult and confirming impetus came at his farm when one of his Scottish highland cattle lifted "a whole snake fence with its horns."

Soon after, Shaw-Rimmington had 30 tonnes of glacial till delivered to his farm and began teaching himself the craft.

"I learned how to place stones wide enough so they lean in, how to use hearting for friction and support. It's like a tapestry or weaving of smaller flattish stones that make everything fit and not jiggle. It's always the heart that matters, the inside that counts. For every outside stone, there are 20 little ones inside."