This section is from the book "The Boy Mechanic Vol. 2 1000 Things for Boys to Do", by Popular Mechanics Co.. Also available from Amazon: The Boy Mechanic, Vol2: 1000 Things for Boys to Do.
To facilitate the running of electric wires through curved fixtures, nick a heavy shot, A, and fasten it on a cord,
Ill: A Shot That will Pass through the Fixture Arm will Carry a Cord for Pulling in the Wires
B, in the same manner as a fishline is weighted. The shot will roll through the fixture tube, carrying the cord with it. A cord strong enough to pull the wires through can be easily drawn through the opening in this manner. The shot should, of course, not be so large that it can possibly bind in the tube.