Set the plastic window well cover over the well opening. Check that the cover is seated over the well opening with a 2-inch or less overhang and that the hinge is pressed firmly against the house wall.
Place the tip of the felt-tip marker through each predrilled hole in the hinge to leave a visible mark. There should only be one hole at each side of the hinge for anchoring. Remove the well cover once each hole is marked.
Measure down the tip of the ¼-inch masonry drill bit 2 1/2 to 3 inches with a tape measure. Wrap a piece of tape around the shaft of the bit so you will not drill holes deeper than the anchor fastener that you're using. Insert the masonry drill bit onto the drill.
Drill holes into the foundation of the home at the points where you made the marks with the marker. Stop drilling once the tape reaches the foundation wall. Clean out each drilled hole with a ¼-inch to ½-inch pipe brush.
Place the hinged cover back over the well opening. Line up the holes in the hinge to the ones drilled in the foundation wall. Place a ¼-inch by 2-inch-long masonry anchor into the hole. Thread the anchor into the wall with a drill fitted with a 5/16 hex bit. Stop tightening the anchor once the hinge is flush to the foundation wall. Repeat the process on the opposite side to complete the installation.