Apologies if it has been raised before:
Years gone by I used to carry a letterman or large Swiss penknife in my flight bag. I could take many things apart; not always put them back together again. However, en-route or on the ground in some out of the way place I have been able to effect repairs to simple things. No longer possible. But then I saw an engineer in the flight deck with a letterman. He told me he was allowed by security to bring it through as it was part of his necessary tool kit to do his job. I tried this argument at security and 'the jobs worth' said no way. Who's he to say what is necessary for me to do my job or not?