The wear and tear of everyday life can make even the sturdiest chair unsteady. But don't get mad, get even--get your chair's legs even, that is. Simply sand away the unevenness, and it's almost as good as new. See How to Fix a Wobbly Table for more ideas.
Place the offending chair upside down on top of a plastic tarp or drop cloth.
Carefully measure the length of each leg to determine the wobble maker and its length (see A).
On the other three legs, make a pencil mark at the same length as the wobbly one.
Gently sand each of the longer three legs until you reach the pencil mark, starting with coarse (80-grit) sandpaper and ending with fine (220-grit) sandpaper (see B). It's best to sand outdoors to keep the fine wood dust particles from permeating your home.
If the chair has metal, cork or plastic glides, check the legs to make sure one is not missing. If a glide is missing, buy a replacement one at a hardware store. Glides are small disks used to protect floors from furniture.
If one chair leg is 1/4 inch (6 mm) shorter than the other three, consider placing a glide on the shorter leg to make up the difference instead of sanding down the other three legs.
Examine the chair joints--loose ones will cause the chair to wobble. Reinforce a loose joint with wood glue (see How to Reglue Joints of Chairs and Tables).