Felting needles are barbed needles used to interlock wool fibers. As the felting needle is moved up and down, the barbs on the needles catch the scales of the wool and entangle them creating a material called felt. The 38 gauge star needle is a four sided needle that leaves a smaller hole in the felted surface. It felts slower than the larger gauge triangle needles, but the detail is finer. Triangle needles are three sided needles. The 36 gauge is used for faster coarse felting that leaves a larger hole in the felted surface. Th e 38 gauge is a general purpose needle used for medium felting that le aves a smaller hole than the 36 and is good for attaching felt to felt or to wool. The 40 gauge is excellent for fine detailing and sculpting.