Fred Kretchman stood next to his display of handmade bamboo fly rods and patiently explained his manufacturing process. First he treats a length of seasoned bamboo with an open flame to get a dark brown hue. “Like toasting a piece of bread,” said Kretchman, of Kittery Point. Fifty hours of labor later, the fishing rod is complete. Kretchman was one of 100 fine craft artisans peddling their wares Saturday at the Maine Crafts Association’s Portland Fine Craft Show along with hundreds of artists at the 51st WCSH Sidewalk Art Festival.