Answer:
A device for finding furniture in the dark.
Thirty white horses on a red hill, first they champ, then they stamp, then they stand still.
The eight of us move forth and back. To protect our king from the foes attack.
I am free for the taking. Through all of your life, though given but once at birth. I am less than nothing in weight, but will fell the strongest of you if held.
It has no top or bottom, but it can hold flesh, bones, and blood all at the same time.
I met a man on the London bridge, he tipped his hat and drew his name, in this riddle I told you his name. What is it?