A redstone contraption is set up as seen in the first screenshot. The bottom layer is just a button, block and redstone torch to alter the state of the (sticky) piston. This alone will work as expected (the piston is in an active state except when the button is pressed). However, when the next two layers are added, pressing the button will not deactivate the piston and once you have pressed the button (and waited for it to depress), you can remove all other blocks around the piston and it remains in an active state (like in the second screenshot).