The Select Previous Layer command selects the
layer just above the active layer in the layer stack. The command
highlights the layer in the Layers Dialog and makes it the new active
layer. If the active layer is already at the top of the stack, this
menu entry is insensitive and grayed out.
Note that on a standard Windows-style English keyboard, the default
shortcut Page_Up does not refer to the key on the
numeric keypad, but to the other Page_Up key in the
group of six keys to the left of the numeric keypad.
The keyboard shortcuts for
Select Previous Layer and
Select Next Layer may be very useful if
you frequently pick colors from one layer to use for painting on
another layer, especially when you use them with the color-picker
tool, which you get by holding down the Ctrl key
with most of the painting tools.
Activating the Command
You can access this command from the image menubar through
Layer->Stack->Select Previous Layer,
or by using the keyboard shortcut Page_Up,
or the “Up-arrow” key,
or simply by clicking on the layer name in the Layers Dialog.