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Tool - Self leveling Laser

Self leveling laser 

DeWalt DW087K LaserChalkLine Self-Leveling Line Laser (Horizontal & Vertical)

Available for about $155.

http://www.amazon.com/gp/product/B000BK32EA/ref=ox_ya_os_product 

For outside use it is also worth getting some red glasses

http://www.amazon.com/DEWALT-DW0714-Laser-Enhancement-Glasses/dp/B00093DJ4M/ref=pd_bxgy_hi_img_b