I know that when building an eruv, the string has to go over the top of the lechi (pole/upright). This document had some great illustrations.
I'm just curious, which method is most durable? Which is usually used? (They show one of a string wrapped around a nail; could I drive the nail/thumbtack all the way into the wood? How often is the loop-over-then-through-a-hole-below-the-top used?
By the way, what material makes a good eruv string? Twine? Fishing line? Nylon?