Bill filed notches into the bottoms of each leg and the base of the pier. One notch for the first leg, 2 for the second and 3 for the third. I think his intention was to ensure the same leg went in each position each time. This probably allowed quicker polar alignment if nothing changed between setups. Also, the notches could be easily felt in the dark.

You'll notice in the photo that Bill attached a cotter pin to a string on each leg. The pin fits in a hole drilled through the leg and pier. The purpose of this really perplexed me. I think the user would insert the pin and expand it inside the pier to prevent the leg from falling off accidentally if the pier was picked up and the thumb screws holding the leg on had loosened up. Just a guess.