Mix approx. 1 tablespoon of the 2-part epoxy, following manufacturers instructions.
     

     Coat one end of each 2 1/2" threaded pin with epoxy.
     Insert the pins into the holes, making sure that there is adequate epoxy to anchor the pins securely.
     Insure that the pins are perpendicular to the surface of the address block.

     Allow epoxy to cure according to manufacturers directions.

     Remove existing house numbers.

     While holding the address block in the desired position, mark the location of one of the mounting pins.

     Using a hammer drill and 1/4" masonry bit, drill hole in the location marked previously (depth of approx. 1 1/2").

     Using a tape measure, measure the distance center to center of the pins mounted in the address block. 

     Using the measurement obtained in the previous step, mark the location for the second hole, insuring that the address block will be level.

     Using a hammer drill and 1/4" masonry bit, drill hole in the location marked previously (depth of approx. 1 1/2").

     Hold address block to wall, and check for hole alignment with pins.
     If both pins cannot be inserted, and allow the address block to lie flat against the wall, elongate the holes to accommodate the pins.

     Using an air blower or vacuum, remove the dust from the holes to ensure proper bonding.

     Using either 2-part liquid or kneadable epoxy, apply liberally to the two pins.

     Put block in place, carefully aligning pins with the holes.
Press firmly to insure the block is completely in contact with the wall.