Woodpeckers Fat Head Hook Rule features a positive physical reference locating the zero point of your rule exactly at the edge of your stock. It's the only hook rule on the market where your rule lies flat (all the others require you to hold the rule upright). Don't fumble with aligning the end of your rule to the edge of your stock. Just use a Fat Head and you'll know for sure that you're right on. Even if your stock has a round-over on the edge (like standard framing lumber) you're always calibrated perfectly with the primary edge.
This rule is the 150mm model. It is also available in 300mm and 450mm.
Note that some images serve as range illustrations and may not reflect the actual models and quantities. For an accurate depiction, see the first image on a white background.