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.
Thinking [in terms of loops and arcs] allows us to let go of a specific journey or sequence, and imagine dozens of scenarios and possible sequences in which these skills can be learned. This doesn’t mean there aren’t more fundamental skills that other skills build upon, but we can let go the tyranny of how, precisely, a person will move through a system. We’re free to zoom in and obsess on these loops, which does two things for us:
Approach the design of a system as the design of these as small but significant moments of learning.
Consider the many ways these loops might be sequenced, with the exact order being less important.