Oh this is fun, due to it’s nature. A noun and verb, gliding on the use of nomenclature. It looks the same both front and back, From letter sequence, to on the rack. A calming paddle forth and back, To places boats can’t take you.

I’m the most useful thing to own, on beaches far or trips unknown. I dry, I wrap, I sometimes sprawl, what am I, beloved by all?

First word is one less than ten; the second, A four-letter measure used metric and imperial then. The last is pounded hard into a wall, To keep something fixed, or hang it tall. Three words together, a band of repute; My lead singer, Reznor, resonates with many a techno fan.

I surround the castle, deep and wide, Keeping foes away with watery pride. What am I?

Notice me and see how I sit atop all the chaps, Guarding pates from sun's hot slap. With a brim so wide, or non-existent and narrow, I crown thee a stylish shield, so no need to bellow!