The angle at which your hands rest while typing makes a big difference. Some people find that laying their hands on a completely flat surface isn't so comfortable, over long stretches of time. This is where the Tilt/Tent Kit comes in.
The kit is composed of six custom-built aluminum legs with spring-loaded finger screws. These screws fit into knurled reinforced metal inserts in the body of the ErgoDox EZ. With the kit installed, you can tilt your ErgoDox EZ and incline the keyboards towards you or away from you. You can also tent the keyboard by angling both halves away from each other, creating a "roof" shape that matches the contour of your hands as you rest them.
There's a rubber foot at the bottom of each tilt/tent leg, so the keyboard won't slide around on your desk. The way it locks into the keyboard is extremely sturdy, thanks to the metal-to-metal connection where the legs "mesh" into the body of the keyboard. Extreme comfort, here we come.