Make seven copies of the last made layer and choose the usual
Free Transform selection to place the copies as it is indicated next step.
Next we’ll try to represent the ditch on the screw’s head, choosing the
Rectangle Tool (U).
The layer’s parameters:
Blending Options>Inner Shadow
Blending Options>Color Overlay 
Blending Options>Stroke 
Make seven copies of the last made layer, reserved for the screw’s ditch and apply the
Free Transform option to turn the copies over if necessary and place them the way it is demonstrated next picture.
The abstraction is finished!
View full size
here.
