4142 HT Alloy Steel machined for perfect accuracy and repeatability.
This vee block design works quite well squaring the bolster face of integral bolster knives for a perfect fit up with the handle.
As with all of Behnke guides, the C2 Carbide Blanks are Surface Ground ! With this being ground, it assures that the surfaces of the bolster are in the same plane to mate up with the handle.
It’s a tremendous time saver when making bolstered knives.
 
These file (or grinding) guides are made from 4142 HT Alloy Steel, both with 3 pieces of C2 Carbide.
 
The pins are  1/4-20 socket cap screws are 1 3/4” in length and supplied along with an Allen wrench.
 
The carbide is not affected by abrasives other than the diamond.