This is used to make an "exact replica of a disk or partition, probably for the making of bootable CDs." He used this clone option to make an image of the OS X 10.1 .dmg file to an empty partition ...

His app automates the process of making a bootable install disk for both Lion and Mountain Lion—just run the app and let it do its thing.

Or just save a copy of the DMG file after download pre-install and restore it to a USB stick.