Drill holes can mean several things. It depends on how they are arranged, first you must know if they are in a horizonal or vertical surface, each is a different meaning. By themselves drill holes are virtually useless but used in conjuction with other symbols, normally found nearby, they can lead to heart stopping surprises...In one case, also in AZ, the find was a lot of gold, in another case in TX they directed an unknowning victim to a explosive death trap, the powder burns are still visible on the cliff face. Amazingly the drill holes are seldom of Spanish origin. Most have to do with far more recent activity.