Graduated slide rule extends up to 6"
Slide rule runs under friction in T-lot and stops at each end to prevent sliding from falling out
X46X has two 6" extension slides: an extension is ready for use on the first section
HX46 has hook zero falls at inside of hook, for distance measuring
X46F has flat, inside markings: numbering begins on inside of rule
For carpenters and other professional craftsmen