#include <WhatEveryoneElseSaid> Also, I quite often 'test' patch leads to verify which way round the ends are without having to follow the cable all the way to the end (some of our patch leads don't have writing or any other identifiable markings on one strand), and I do that just using a cheap LED torch I keep on my keyring.. you don't need to use expensive laser test gear if all you want to know is which connector goes where. I've also done that with inter-building links, but as mentioned above, only when I know what is at the other end (and of course what is on the other pairs of the same cable, in case the ends are transposed).