Dowels harvested from wood including portions from adjacent growth rings that are oriented so that the dowels expand in a horizontal direction, relative to its longitudinal axis, when exposed to moisture. Assembly systems can incorporate the dowels as fasteners, dowels and the assembly systems marked to allow for orienting the dowels for expansion in a predetermined direction relative to the assembly system. Wall systems made of contiguous wall panels assembled with dowels, where the dowel paths are arranged in configurations for stabilizing the assembled wall system. The wall panel tops can include pairs of dowel paths angled toward each other. The central wall panel bottoms can include a dowel path along a longitudinal axis, while the flanking wall panel bottoms can include dowel paths extending toward the central wall panel. The wall system can include the markings for orienting marked and directionally-expanding dowels.