I definitely should have read the reviews before buying. As others have said, there is no precision with this device. There are at least two oblique axes - the first is the angle between the block and the alignment line on the plastic window. It can be manually retracted to 90 degrees and easily moved while drilling. The second is the size of the pilot hole - it's too big and doesn't fit neatly in the drill. All this leads to a terrible seizure.