Figure 2: The first seven modes of vibration for a bar with two free ends
(Fletcher and Rossing p. 536)
Notice in Figure 2 that the two holes in the bar, used to suspend it from a cord in the air, are placed at the nodes of the first mode. Placing the cord anywhere along the bar will have a slight damping effect on any mode whose antinode corresponds to its location. At a node, however, where no displacement occurs during the transverse vibration, the cord would have almost no effect. Therefore, placement of the holes at these locations ensures that, while some of the upper partials may lose their strength, the fundamental's vibrations go unhindered by the slight damping effect of the cord.