1. Find a straight line on the putting green of about 10 feet. You want a putt with no break.

2. Place one of the 3-inch nails in line with direction you'll be putting. When you push the nail into the ground make sure it's high enough for your putter blade to fit under.

3. Place the other 3-inch nail about 10 feet from the other nail in line with the direction you'll be putting.

4. Tie the string to both ends of the nails making sure it's tight enough so that the string doesn't sag.

5. Now draw a straight line completely around the center of your golf ball with the Sharpie. One of those tools for creating a line on your golf ball works best.

6. Next set your golf ball down next to the string near one of the nails with the line on your golf ball parallel to the string.

7. Finally strike the golf ball along the line of the string. This will require your putter head to slide underneath the string to be able to strike the golf ball solidly. If the golf ball wobbles then it means you hit it of center. If the golf ball doesn't wobble, but goes away or into the string then it means your alignment is off.

This drill provides immediate feedback if your not striking the golf ball on the center of the putter face.

You can do one more thing with this drill to help you take the putter straight back. Take 2 golf tees and place them perpendicular to the string at the location where you're striking the golf ball. You want the tees to be barely wide enough for your putter head to fit through. At first you may want to give yourself a little more space for your putter head to fit through, but you should eventually move the tees as close as you can.

It won't take long with this drill to get you striking your putts squarely and solidly every time. You can carry these items in your bag and set it up any time while at the practice putting green. You'll probably draw the attention of other golfers because they'll be intrigued by your ingenious putting rig.