You may want to extend a putter if you're tall and you feel you are reaching too far down to grip the club, or if you want to promote an open-square-closed stroke such as the one promoted by putting teacher Stan Utley and used by Tiger Woods.
To extend the putter is a fairly straightforward process. It uses a metal or plastic plug which is glued into the shaft, then the grip goes over the top. It's something you can do yourself with minimal tools or skill, but it will save you money.
There are just a couple of safety considerations to take into account (please read these instructions carefully, especially the parts in bold), but otherwise you need no particular skills, but otherwise you need no particular skills to extend a putter yourself:
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Here's the equipment you'll need to extend a putter...
      A utility knife
      About 30fl oz (100ml) of solvent
      Double sided grip tape (usually supplied by grip retailer)
      A cloth
      A metal or plastic shaft extension plug (available from grip retailers)
      An epoxy resin glue (available at all hardware stores)
      A marker pen
      A metal pipe cutter
      A bucket
      A new putter grip
How to do it...
Step 1: Cut off the old grip:
Before you can start to think about how to extend a putter, you have to get rid of the old grip... Using a utility knife start at the bottom of the grip and cut straight through, always moving the knife away from you. The safest way to do this is in a vice using a rubber shaft grip.
Step 2: Clean the area of the shaft under the grip:
Scrape or pull away all the old double-sided tape from the grip area. If you are going to use the knife again, make sure you move the blade away from you.
Step 3: Wipe the shaft totally clean:
To make sure the whole of the shaft is clean, put some solvent on the cloth and wipe the remaining bits of tape and adhesive away. The shaft should be totally clean before moving on.
Step 4: Glue in the extension plug:
Follow the instructions on the glue to fix the grip extension in place in the end of the shaft.
Leave to dry for the required period. Do not scrimp on the amount of glue you use, but make sure you wipe any excess off!
The epoxy resin used to extend a putter can take longer than you think to dry. You're best off leaving it overnight (at least) to fully cure hard.
Step 5: Cut the shaft to the required length:
After allowing the glue to dry fully, measure the length of shaft you want and mark that point with your marker pen (some plastic plugs used to extend a putter may have 1/2 inch markings on them). To allow for the extra length added by the grip, cut the shaft using the pipe cutter at a point 1/3 inch (0.75cm) shorter than the point you have marked off.
The pipe cutter works by clamping the shaft against a blade which scores and eventually cuts the shaft as you turn the cutter around it. Right from the start tighten it nearly as much as you can and keep rotating the cutter until the excess piece of shaft breaks off completely.
Step 6: Wind new tape around the shaft:
Grip retailers normally send a length of special double sided tape with each new grip.
Carefully wind the tape down the grip in a spiral shape.
Tape straight over the join between the end of the shaft and the extension plug.
Make sure that the tape is evenly spaced and that it doesn't overlap. For regular grip thickness, leave a gap between each wind of tape, as in the picture. Tuck the excess tape into the end of the shaft to seal it up.
Some grip tape is extremely wide (2-3 inches). If using this kind of tape, stick a single length vertically onto the shaft and fold it round, so that the shaft is entirely covered.
Step 7: Slip the grip on:
Firstly remove the back side of the double sided tape wrapped round the shaft.
Then take the new grip and pour some solvent into it, holding your finger over the hole in the butt end to stop it leaking out. The solvent allows the grip to slip over the double sided tape and activates the adhesive in some tapes.
Next, with a finger over the holes at both ends of the grip, turn the grip this way and that, and then upside down to ensure that all areas of the inside of the grip are well washed with solvent.
With the bucket underneath to catch the excess, tip the solvent from the grip out onto the double sided tape which covers the shaft.
While it is still wet, line up the flat front side of the putter so that it's roughly at right angles to the putter face and slip the grip over the shaft.
There is a knack to doing this - you have to firm and fairly fast, and remember to push with both hands - putting the toe end of the putter against a wall will help.
(If you're really struggling you probably haven't got enough solvent on the double sided tape, or on the inside of the grip).
Make sure the grip is pushed fully onto the shaft by holding the putter head and putting the butt end of the grip on the ground. Push down firmly to ensure the grip is as far onto the putter shaft as possible.
Final Step: Ensure grip is properly aligned:
Put the putter the right way up again and look down the flat front surface of the grip to check the alignment. If the face of the putter appears not to be at right angles to the front of the grip, move it carefully round to the right or left and then check again. Repeat until you're happy with the alignment.
Also, be sure to check that the grip is straight on the shaft down its entire length and not twisted. Once you've done that you're done - that's how you extend a putter. All you have to do now is wait for the adhesive in the grip tape to dry.
The drying time for a putter grip in warm weather is about 4 hours.