Not all the towers along a transmission line are identical. Look closely at a tower where the line makes a sharp turn and you will likely find it is wider and beefier than other towers along the route. The added strength and weight are needed to resist the unbalanced pull of the conductors, which might overturn an ordinary tower. These special towers are called deviation or angle towers.
The transmission-line tower everybody knows is an Erector Set latticework of steel girders and diagonal braces. The techniques for designing and building these towers are the same ones used in constructing steel bridge trusses or crane booms. The individual pieces can be made cheaply from rolled steel and then bolted together on the site. This last point is more important than it might seem: transporting a fully assembled tower 100 feet tall is an awkward and expensive business.
Through the ages, the professional users of tools by and large have not needed to, been able to, or wanted to talk to outsiders about their implements. They did not need to because tools themselves are used to make other tools, and thus users could very often fashion a new tool with their old ones. If they did need to communicate the design for a new tool to someone outside their trade, they could do so without having to reveal the tool's intended use...Besides, the inventive process of conceiving a new tool was often a nonverbal one. Finally, craftsmen were unwilling to share information about their specialized tools because to do so would have been to give up their competitive edge and their value to those outside the craft.