I'm talking about the home-made 'shadow boards' that you'll find in workshops, suburban garages and tool sheds all over the land. Usually made from a standard-size section of peg board, often sealed with paint left over from some other interior decorating job (avocado green from the kitchen, perhaps, or lemon yellow from the bathroom do-up). And then carefully inscribed with the shapes or shadows of all the key tools in the arsenal: hammers, wrenches, saws, etc..

In Sydenham right now, Christchurch Art Gallery and Gap Filler are working with local artist Wayne Youle to create the biggest shadow board you will see anywhere (I know I railed against exaggeration the other day, but it really is the biggest). Over the next couple of weeks you can watch it growing day by day on a colossal wall at the 'gateway' to Sydenham, on your left on Colombo Street just over the Moorhouse overbridge. There are progress reports here and here, and here's a section of the design itself...

When Wayne was first invited to create a mural for Sydenham, he thought about what the suburb means to him. Youle loves to make art with a crisp and pristine finish, and Sydenham is a place he often goes to work or consult with local tradespeople when creating a new work of art. The side streets of the suburb boast what must be the city's densest concentration of upholsterers, sign-makers and automotive painters – people who make 'finish' their business. At the same time, of course, Wayne was thinking about the suburb's post-quake fate – about the grievous blow dealt to so many of its humble and character-rich brick buildings.

And all this led Wayne to the thought of old-school shadow boards and their silhouetted tools. Hammers, wrenches and saws all appear on the board Wayne's designed for Sydenham, but there are also some tools like shovels and sledgehammers that have a special local resonance (silt to shift or walls to topple, anyone?). The real surprises on his board, however, are the shadow images of dozens of familiar things – among them cameras, wedding rings, a teddy bear, a guitar, a toilet, and even a house.

Wayne says: "I thought of the number of things that are missing or gone for good after the earthquakes. Things that hold not only financial but personal value. These things may have gone, but there is also a 'fix-it' attitude in Sydenham and in Christchurch. This is why there are tons of tool silhouettes. They are being used for the re-build of something, be it big or small, for one or for all."

Now that quite a few staff at the Gallery and Gap Filler have seen the design, it's clear people are going to enjoy finding their own favourite 'shadow' on the board. But I suspect the key shadow might be the funny-face mask that appears near the centre of the work – a suggestion, maybe, that a sense of the absurd is a crucial post-quake survival tool. Wayne's title for the work appears to bear this out: I seem to have temporarily misplaced my sense of humour.

So come and see it grow. And while you're in Sydenham, check out Gap Filler's community Chess Set just a stone's throw along Colombo. (And while we're here, a big thanks to David Wagner and Wagner Holdings, Mike Jones, B&F Papers and VINZ Sydenham.)