During the off-season and really throughout the year, many golfers want exercises and drills to do inside to sharpen up their putting. Obviously, you are pretty limited indoors by space limitations and also by the nature of the surface (flat, carpet, no break). Still, if you focus on the perceptual and movement skills that are fundamental to golf, you can get a lot of valuable practice in. The trick is to focus on developing specific aspects of the art of putting.
Some Theory
While it is generally true that practice conditions should closely simulate actual playing conditions, the purpose of this rule is to train your response to stress and to present the same variety of problems you face on the course. But fundamentally, your skills in putting develop separately and come together over time like a slowly developing photograph. There are many different perceptual and motor skills in putting that need to function cooperatively in an integrated way, and these aspects develop independently at differing paces. An indoor practice regimen that focuses on developing these isolated aspects of putting can speed up your advancement quite nicely.
In the psychology of learning, it is important to consciously identify the aspect of a sport you are practicing and to understand its function in the total mix. This allows you to monitor your practice for relevant performance cues and feedback. As a consequence, your learning proceeds faster and your skill develops with greater definition and staying-power and is more readily available in memory storage for accurate activation later on.
Some Exercises
1. Floorline Putting. An excellent exercise that combines a number of these skills is setting up over a linoleum tile floor, using an intersection of tiles as the ball, and then sighting along the floor line for the puttline. The intersection lines allow you to sense a square setup better, as you can see the distance of your toes to the line, see the cross-line perpendicular to the puttline as it establishes ball position a little forward of the middle of your stance; see the approximate relationship of a balanced stance on either side of this cross-line; see whether you flare your toes outward; match the floorline with a line horizontal across both eyes; detect in your head-turn to the target whether your head is propelling your gaze off line; calibrate the extent of your neck turn to the target with various well-defined distances; use the puttline behind the ball to monitor your takeaway and backstroke; use the puttline in front of the ball to monitor your throughstroke, etc. All together, this is an excellent exercise. If your experience is similar to that of many others, this exercise will feel odd as you turn to the target, because you are not used to keeping your gaze steady and then moving the gaze down the line. Most golfers jump from the ball to the target, skipping the in-between. And the changes that occur in gaze and head orientation in such a technique cause misperceptions that go unnoticed. The floor drill helps tremendously with these aspects and problems.
2. Doorjamb Gazing. In order to sense a straight-out-of-the-face gaze and become familiar with the relevant cues of your field of vision, you can stand a bit away from a doorjamb and gaze dead level to a spot that is the same height as your pupils. To see this height, stand next to the jamb with good posture and simply note with your thumb on the jamb how high your pupil is. Mark it if you like. Then back away and work at a balanced, erect posture with no tilt in your head. Close your nondominant eye and note where in your field of vision this aim spot occupies. It should be approximately one inch in from the bridge of your nose level with a horizontal line across both pupils. Set the back knuckle of your thumb on the bridge of your nose and see if the aim spot is not just off the tip of your thumb. This is the location in your field of vision you use when sighting, either sighting the target from behind the ball, looking at a dimple on the back of the ball, looking at an aim spot on the ground, scanning along the line of the putt, looking at the back lip of the hole from the address position, and so on. It helps to know whether you are actually using this focused vision in sighting these points by becoming familiar with the "look and feel" of proper use of the gaze. Otherwise, your eye control is likely to be poor. You can also practice this gaze control in front of a mirror, by looking straight and level into your dominant eye's pupil.
3. Ruler Putting. Put a yardstick on the floor and make strokes above it. This is an old Horton Smith training trick that helps coordinate the visual monitoring of the stroke with the feeling of a straight stroke. You will have a problem with this exercise unless either your hands are directly beneath your shoulder sockets at address or you know how to "hood" the stroke in response to "gating" caused by having the hands positioned inside or outside the line beneath the sockets. You can also place a ball on the yardstick and putt it off the end.
4. Chase the Rabbit. Putt one ball away (see "The Core Putt" tip) and then putt a second ball at this "rabbit" so the second ball just barely touches the first. This drill trains targeting and coordinating targeting with movement planning and consistent tempo.
5. Fill the Sleeve Box. Place an empty golf ball sleeve box on the carpet about 8 to 10 feet away and putt a ball back into the box. Then putt two more balls into the box. This is a neat trick that forces you to really focus on line and distance / force control. It's easier than it sounds!
6. Knock the Ball into the Target. Set a ball about a foot short of a target (salt shaker, checker?) and then back off about 8 feet and putt a ball at the first ball so that it gets knocked straight ahead into the target. Anything off line and the two-ball collision will send the stationary ball off on an angle.
7. Align the Face. Mark a target about 10-15 feet away and use a small wooden block as the putterface. Set the block behind the ball and, standing at address, move it until it looks aimed at the target. Then walk behind the block and check it with your dominant eye. See if you have any persistent misalignment tendencies.
8. Putt Two Balls. Set two ball down so they both fit within your putterface as aimed at a target, with the saweetspot directly behind a small gap between the balls. Make a stroke that contacts both balls at the same time, and sends both off on a straight line. This exercise tests your ability to make square impact, without putterface twists, and gives immediate feedback. A variant is to putt an empty spool from a sewing kit, contacting the two "wheels" at the same time with the face.
9. Nudge the Ball. Set or balance a ball on a penny and putt a second ball to this ball so that it just touches the first, but DOES NOT knock it off the penny! This one is SUPER TOUGH! Try various distances. You should soon forget about the line and "making" the putt -- distance control is everything, and rolling the ball to the target with an acceptable "sink" speed becomes second nature as you try not to knock the target ball off the coin. A variant is to putt to a tee set upside down on the carpet, or to putt to a metal putting cup with levering edges so that the ball climbs the edge but falls back.
Make This Part of Your Game
There are many, many exercises like this that can be devised to focus practice on the relevant perceptual and motor skills in the art of putting. Make up your own, so long as the exercise highlights an important perceptual or motor skill fundamental to putting. And when you get on the practice green, put these drills into effect again. But on the course, your only job is to sink the putt.