The weatherproofing material is the topmost or outermost layer exposed to the weather. The topmost node in a tree is called the root node. The insulating layer and topmost silicon layer also vary widely with application. Towers have thicker girth in the lower levels, progressively narrowing to the topmost level. Decomposition of organic material causes boron to be deposited in the topmost soil layer. Small greenish yellow flowers sit on the ridges of the topmost segment. The rearmament became the topmost priority of the German government. Being the topmost node, the root node will not have a parent. User applications usually deal only with the topmost layers. Indeed, transit routers typically need only to examine the topmost label on the stack. The three place the sleeping princess on a bed within the topmost tower. Until the topmost voussoir, the keystone, is positioned, the vault is not self-supporting. The topmost card of each pile is turned face up. Words operate directly on the topmost values in the first of these two stacks. It had three concentric defensive walls surrounding the inner, topmost ring.