Cable Tool
Imagine that your hand is a drill bit. You’re on a large pile of firm sand, sand that is damp. You’re going to use your drill bit to get down through the sand up to your shoulder. You’re going to use your drill the way a cable tool rig uses it. That is to drive your fist straight down into the ground. In your case, you’re pounding your fist into sand so that you don’t hurt yourself, but imagine that you’re going through dirt and the rock layers under it.
You continue to drill by going up and down, pounding down over and over. What you may find is that the bottom of the hole gets clogged up with sand that falls in from the sides. Now imagine using your other hand as a scoop. Reach down into the hole and scoop up the loose sand. Do that until all of the loose sand is out.
Switch back to you’re your other hand that you’re pretending is a drill bit. Continue to pound your way straight down through the earth.
What you are doing is what a cable tool rig does. The driller is hoping to drill down to a layer where there is oil. What would be really nice is if the earth were pushing on the oil and that would cause the oil to come up to the top of the hole all by itself.
Information provided by Walter Eskridge, Curator of Education