One of the many benefits of doing this series is that it requires me to spend some time each day looking over a few photos, which not only requires me to review what I know about the location, but also, inevitably, raises new questions. On occasion, following photos can give me an insight into answering some of those questions. Had you asked me yesterday or the day before what the purpose of the I-beams (three of which were torn out during the tsunami; above is the one remaining) on the ends of the dock, I would've guessed some kind of spacers. But the photo above suggests a slightly different purpose. It still has a roller attached to it. Imagining the others had a similar configuration, I picture four sturdy poles, one at each corner, anchored in the harbor floor. The pairs of rollers on each corner would allow the dock to move up and down with the tides, but constrain horizontal motion, exactly as commenter Skinny Dennis said on Tuesday. At least until the great wave hit.