Through bolting changes the way tray panels joint each other and eliminates tray ring clamps completely. Between tray panels, bolts go completely through each tray panel. At the tower wall, the bolt goes completely through the tray panel and the tray ring. Through bolting has a minimal equipment cost. The major equipment item is that the tray fabrication tolerances are now much tighter. The holes between each tray panel must line up without slop. As a practical matter, the best way of getting the holes in the right place is to field drill them rather than depend on vendor capabilities.
Field drilling is also required in tray rings when through
bolting existing towers. Field drilling adds time and cost. Through
drilling is the single largest cost in reinforced tray designs.
However, it also adds the most strength.