Our sharpening ruler includes a small "hook" on one end so that it catches on the sharpening stone to help the ruler not slide around. 

The most innovative technique in plane sharpening over the last 35 years is the "ruler trick" by David Charlesworth. Traditionally, a sharp cutting edge is achieved by honing the back of your plane blade until it is dead flat (this takes hours), then you hone the primary bevel to achieve a razor sharp edge. 

David Charlesworth introduced his ruler trick to save significant time while still achieving a razor sharp edge.  Instead of flattening the whole blade back, he placed a thin ruler on the stone raising up the blade about 1 degree, effectively flattening the blades' leading edge, not the whole back.  David's "ruler trick" works great.

We custom make our sharpening ruler specifically for the "ruler-trick" 

Product Details:

• Length: 10-1/2 inches (267mm)
• Width: 1/2 inch (13mm)
• Thickness: .020 inches (.05mm)
• Hook: Sits down by .070 inch (1.5mm)
• Surface: No ruler etchings so the blade freely slides back and forth.
• Hanging Hole: Small hole at one end to hang the ruler.