A dictionary (三省堂の『例解小学国語辞典第5版』) definition of 棒:
???? long and thin wood, bamboo or metal.
I'm stumped on the first part of this definition. I have 持てるくらいの長さ = "Length to the extent that it can possess". Possess what?
And what is the following の? My guess is that it marks possession, i.e. each of wood, bamboo and metal have the property which is 持てるくらいの長さ. When I try and put all this together I can't get anything that makes sense.
If I had to guess the meaning I'd have said it means "Wood that possesses length" but I'd have written that as 長さを持っている木. Besides which, that's a terrible definition. The key characteristic is that it is longer than it is wide, but I can't see any way that it could mean that.