I made a bunch of tool organizers for my workshop, but was having trouble getting the correct hole diameter for things like screwdrivers, etc.  So I made a hole sample block with various hole diameters so I could print it out and use it for reference when designing tool holders.   Holes are in decimal fractions of an inch, in .02" increments from .02" (really .04 due to printer resolution) to .5".  Block is 4.5" square and ½" thick.