I might hold up a fence or hold up your news, deliver your letters or carry your views. Buried in dirt or living online, what one small word fits all three just fine?

I'm an artsy sort, You can finish me with ball or brush, Or start me with finger or face, What am I?

I hold the bird that sings no more, Yet warriors clash behind my door. Prizefighters test their might, In my squared ring, day or night. What am I?

Ahoy, matey! I stand tall on land or sea, A pirate's colors fly high on me. What am I?

A silver serpent crosses the land. Drawing miles of straight lines, sometimes a bend. It never sleeps but lays on a bed. Like stairs taking people up, yet it always stays flat.