After clearing away the biggest part of the rock, crews with air-powered drills made holes close together, then chipped out the intervening rock with chisels and jackhammers. This process is known as honeycombing. The surface of the stone was smoothed with a pneumatic drill and special bit. The crews worked on the mountain using special chairs hung from steel cables.
Eighty percent of the rock was removed with dynamite. The blasting crews were so skilled that they could take out rock to within 4 inches of the final surface.
Borglum used a model carved to a 1 to 12 scale, then used a small protractor on the model and another protractor 12 times bigger on the mountain to arrive at the correct dimensions. A protractor is a clear piece of plastic in the shape of a half moon with the degrees of a circle printed on it.