Use the rulers with a 'lip' and put your name there...
or use something to scratch your name or engrave your name.
I do use Sharpie's on my scissors, tape measures, pin cushions, cutting mats, etc
And if anybody thinks you are paranoid, just say the name is there so YOU can find your things amongst all the others - you are making it easier on yourself - not thinking anyone else is a thief.... besides there are many of the same rulers brought to class/guild so I don't see a thing wrong with having stuff marked - I'd feel terrible if I grabbed somebody else's stuff and waltzed off with it...