Answer:
What is flat, usually square, and made from trees but isn't wood?
What is yours but only used by others?
What never ends but you always have it
If four people can repair four bicycles in four hours, how many bicycles can eight people repair in eight hours?
I usually wear a yellow coat. I usually have a dark head. I make marks wherever I go.
I appear in the morning. But am always there. You can never see me. Though I am everywhere. By night I am gone, though I sometimes never was. Nothing can defeat me. But I am easily gone.