MacBook Pro with Retina display: Do not use palm rest or keycap covers
Leaving any material on the top case (keyboard and palm rest area) could result in damage to the display when you close it. This includes palm rest or keyboard covers, as well as any adhesive-backed keycap additions.
To enable the thin design of MacBook Pro with Retina display computers, the clearance between the display and the top case is engineered to tight tolerances. Do not use palm rest covers or keycap covers, as the additional thickness may interfere with the designed closed position of the display.