The other day I was taking inventory of servers in a data center, and the idea popped into my head for a measuring tape denoted in rack units. This would save a good deal of time when determining the position of a device in an equipment rack, or the amount of free space available. Of course, like nearly every idea I've had, I was not the first. I found a product called Rack Ruler on Amazon for $23.97:
Neat, but $24 is a tad expensive for an obscure tool of undetermined quality. Knowing that a rack unit is exactly 1.75", one could easily repurpose a regular SAE measuring tape by marking it at the appropriate intervals.