To lock down the shaft on a cordless nail grinder follow these steps:

• 1- Press firmly on the thumb lock button.
• 2- Insert the drum rod.
• 3- Continue holding the lock button down, and turn to tighten the spicket nut.
• 4- You should feel the lock button push against your thumb, once it has been properly inserted.
• 5- When you feel the “push”, you can remove your thumb.
• 6- Replace the safety cap before use.

If the batteries are not in correctly it will only work on one speed. It's possible that one battery in the wrong way.

There is a diagram on the inside of the lid that shows you how to correctly install them.

• The stone can be used for filing nails after clipping or to maintain nails done on a weekly or bi-weekly basis.
• The course 60 grit band is used for nails that need a lot of length removed. 
• The fine 100 grit is used similar to the stone.  It takes off a small amount of nail at a time and leaves it with a nice smooth finish.