How to draw a 3D knife

How to draw a 3D realistic switchblade with mixed media on gray paper. 3D drawing by Marcello Barenghi http://www.marcellobarenghi.com
Final picture: http://www.marcellobarenghi.com/2013/04/switchblade-realistic-drawing.html
Materials used:
heavyweight gray paper,
9B, 7B and B pencils (Caran d'Ache grafwood),
paper stomp,
colored pencils (Caran d'Ache Supracolor Soft),
fibre tip pens (Staedtler Noris Club 320 Double Ended Fibre Tip Pens),
markers (Tria Letraset),
watercolors (Ecoline)
black and white acrylic (Decoart and Pebeo)

Time taken 2 hours and 10 minutes
Music by http://www.freestockmusic.com/....2012/pop-production-


This video shows how I draw a realistic knife, coloring with Tria markers, Fibre-tip pens, colored pencils and black acrylic, shading with pencils and paper stomp and, finally, using white acrylic for the light points