A picket fence does not have to look even. It can be uneven just as well. When it is uneven, the sound will be more interesting when the neighborhood boy comes by with his stick to drag along the staves.
Long sticks make low notes. Short sticks make high notes.
Cut the sticks and tune them. Arrange them so a recognizable tune can be played.
Let the boy and the neighborhood discover that the fence has a tune.
Let the Neighborhood discover why the fence is so uneven.
Change the tune each year.
Make a wooden fence in a circle. Tune the interchangeable sticks so you can play a round. Three children running around and clacking the fence at the same speed can play the round.