There has been some debate over wrist rests and whether they do more harm than good. The question really comes back to proper usage, as do most ergonomic questions. If, for example, you buy a a travel pillow and then cock your head awkwardly to use it, it's not really the pillow that is at fault- it's your usage.
The purpose of a wrist rest
As more and more workers type for long stretches at a time, the number of complaints about RSI, such as Carpal Tunnel Syndrome, has gone up as well. That is because most people do not know how to type ergonomically: they drop their wrists to the desk surface, cock their wrists to type, keep the mouse too far away, and do any number of things that put strain on their wrists, hands, and forearms. A wrist rest is a padded strip of material meant to meet your wrists and heels of your hands so that they don't have to drop down to rest. Essentially, a wrist rest catches the heels of your hands so that you don't feel pain in your wrists.
How to use a wrist rest
Ergonomic studies tell us that wrist rests should be used between periods of typing to rest your wrists. So, line up the wrist rest in front of your keyboard so that there is not a drop off between it and the desk. Then, as you type, try to float your hands over the keys and not cock or hyper-extend them. As you pause, rest your wrists on the wrist rest.
How to Choose a Wrist Rest
When choosing a wrist rest, look for the following features: