Digging holes for fencing or other outdoor projects is best done with a post hole digger. This tool is comprised of two shovels attached with a hinge that bite into the soil and allow you to pull it straight up out of the hole. Post hole diggers allow you to dig straight-sided holes without widening the edges of the hole by prying on the soil with the handle of your tool. You can make your own post hole digger using a few common tools and materials.
Roll out your flashing on a flat surface. Place the T square across the metal, 9 inches from the end of the roll. Cut across the metal with your razor knife, keeping the blade against the edge of the T square to get a straight cut. Cut across the flashing several times to score the metal. Remove the square. Bend the flashing back and forth to break it on your score mark.
Fold the flashing into thirds to make a thick band 3 inches wide. Tap the folded metal with your hammer to flatten it and secure the creases in your folds. Cut the band into two pieces, each 3 inches by 8 inches. Drill a hole through the metal bands 1 inch from each end of both pieces.
Wrap a metal band around the handle of one of your trenching shovels, 2 inches above the line where the handle and blade meet. Bend the metal to conform to the shape of the handle. Make the metal ends meet evenly flush on the upper side of the shovel blade, in line with the blade's top surface. Tack the metal to the wooden handle by driving a roofing nail through the metal and into each side of the handle, in line with the wings of the blade. Fasten the second metal band to the other trenching shovel in the same fashion.
Place the tips of the blades of each shovel on the ground. Turn the shovels so the top of the blades face each other and the metal bands you attached to the handles line up. Align the holes you drilled. Slip a bolt through the holes of the two pieces of metal on each side of the shovels, with the bolt heads out. Place a lock washer onto the inside ends of each bolt and twist a nut onto each bolt. Twist the nuts as tightly as possible by hand, then snug them down with your adjustable wrenches to secure the lock washers tightly.
Grasp the upper handles of your post hole digger, lift the tool and stab downward into the soil. Lift the tool, rotate slightly, and repeat until you have a circle of loose dirt that is a few inches deep. Stab the post hole digger into the loose soil, pull the handles apart to close the blades in a pincer action, and lift to remove dirt from the hole.