Right, Tom, no power (ie mechanized) drills in the Monument, for any purpose. Replacement is done by hand drilling. You know how the rock is, so more often than not, old holes cannot be reused. It is essential to place the new bolt as close as possible to the old, especially in height. And crucial to carefully patch the old hole. Clint should address this issue, since he and Bruce have replaced more than 300 bolts there in the last 4 or so years. They are both very skilled at doing so.