Now we have to represent a lateral menu’s panel on the left page’s part. Firstly represent the primary layer of the menu’s panel, selecting the Rectangle Tool (U).

The layer’s parameters: Fill 0% on the layers. Blending Options>Gradient Overlay

Gradient’s parameters:

Divide now the panel of the menu’s button, using the Pencil Tool (B) and represent a dividing stripe:

The layer with the dividing stripe needs the next parameters: Blending Options>Color Overlay