Big Horn 19139 5mm Round Centering Bit (use with Pin Jig). Precisely spaces shelf pin holes 1-1/4", 32mm or 64mm from edges. Index the 20" jig with a shelf pin for use with any length shelf. The Big Horn 19139 is designed for dead on accuracy of shelf pin placement for your project when used with an appropriate template. Our bit assembly is designed so the bit is removable when the time comes that it needs to be sharpened. 5mm self-centering bit can be used with Big Horn 19651 Pin Jig and Bit (sold separately) or other templates with 3/8 Inch guide holes.