What is a clutch alignment tool?

Answer 1

A simple stepped rod which aligns the driven plate centre with the spigot bearing in the flywheel. I've seen them turned from broom handles, sockets of an appropriate size, an old input shaft etc. They're cheap enough and made of plastic these days. You can even hire them. Why is it important? Without it, it is virtually impossible to get the gearbox back on without causing damage to the input shaft and/or the spigot bearing. You could eyeball it but you only get one chance not to foul it up