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.
Design has very little to do with what tools or methodologies you use, or what your job title is, or what you have a degree in, or even anything like “creativity”; design is about your relationship to constraints. Rather: to what extent are you defining constraints rather than just obeying them? Design is about taking a universe of possibilities and converging onto exactly one outcome. Being handed a set of constraints which you treat like immutable laws of physics (because many of them are) and solving within that envelope is what engineering is. To wit: what most designers are doing most of the time is actually a form of engineering, and engineers are always doing at least some design.
This is because genuine design—the power to define constraints—is a privileged political position within an organization, and not everybody can occupy it. In other words, the “seat at the table” comes first. Design is Steve Jobs infamously dropping an iPod prototype into his fish tank, pointing at the bubbles coming out and yelling at his staff to make it thinner. It doesn’t matter what your title is; Jobs is the designer in that scenario.