The beauty of the Swing Align is that you can hit balls with it and get immediate visual and kinesthetic feedback. To get started, slip the padded cuffs onto your biceps. The cuffs must be snug, or the device will move during the swing. (Available in standard size, or an XL version for players with larger biceps.)
With the built-in aluminum rod, you can easily see shoulder alignment at address, shoulder turn at the top of the backswing and swing plane. During the swing, the device will help you feel your arms and body move in unison. The package includes an additional aluminum rod. Lay it on the ground to represent the target line, and use it in conjunction with the rod attached to the cuffs.
The versatile Swing Align also can attach just above the knees to allow you to check alignment and lower-body movement on short-game shots, even on your putting stroke. The XL version works best for the lower body.