Install an electrical box

Electrical conduit should run inside the counter, rather than through the block cells, wherever possible. To install an electrical box on the outside of the counter, cut an opening for the box using a circular saw and set the box in so it protrudes the thickness of whatever finish material you will use.

Drill a hole for the conduit using a masonry bit. Draw a circle for the conduit's hole, drill six or seven holes along its circumference, then chip out the hole using a small masonry bit. Run conduit to the box using an elbow to make the turn. Tap in shims to wedge the box in place. Stuff newspapers into the cell about 6 inches below the electrical box, then fill the area around the box with concrete to hold the box firmly in place.