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.
I wonder how many things we're all going around doing badly because the idea of not knowing how to do them well seems too ridiculous to admit to.
...You've probably never been taught to have a conversation. I've had exactly one class on it and it was in the last six months. I know damn well that many people have not self-taught this well... In general there's this entire class of implicit skills that we mostly don't think of as skills, that we're entirely self-taught on, and that we practice sufficiently non-demonstratively that we can't easily watch what other people do. The result is a very personal skill idiolect.