For most poles you take apart the sections (usually three) and insert the dowels.
Ref poles, yes, there is such a thing as too thin, the spreader bars are subject to compression forces, how much depends on a number of factors such as your weight, the width of the fabric, the length of the pole and the length of the triangles leading from the bars to the apex. If your bridge's dimensions are derived from posts on the forum it may not be a problem, but take precautions your first few times in case the poles aren't up to it.
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Last edited by ExPXGUY; 05-01-2013 at 06:50..
Reason: for clarity