This is should only be used when standing. There are two sets that you can use for the negative incline. For the smaller set, files used should be LeftTop_Keyboard, RightTop_keyboard, Left_Top_Small_Negatvie_Incline, and Right_Top_Small_Negative_Inlince. For the second set which is a taller use the following files:LeftTop_Keyboard, LeftBottom_Keyboard, RightBottom_Keyboard, and Right Top, keyboard. Due to file confusion, please download all the files and for the larger set use the larger base with the larger extender and for the smaller base use the smaller files. Sorry for the inconvience. The model screenshot is an example of set one. The angle on both of these sets is 15 degrees.