Answer:
What do you fill with empty hands?
Scythe of darkness, Shadow’s light. Guiding eye of thirteenth sight.
What I am filled, I can point the way. When I am empty. Nothing moves me. I have two skins. One without and one within.
A hole in a pole, though I fill a hole in white. I'm used more by the day, and less by the night.
In buckles or lace, they help set the pace. The farther you go, the thinner they grow.
What did the piece of wood say when he saw the screwdriver and screws approaching?