This afflicted area has now been patched with an epoxy filler and sanded. The filler is a specialty product that is designed for wood and exterior use. It has a similar degree of elasticity as the wood itself. That is, the filler itself will expand and contract in much the same way as the wood. Thus, these fillers, when correctly used, rarely crack or fail themselves. Although not shown in the photo, large voids can be partially filled with wood that is surrounded by the filler.