Mr Chips i have no qualifications whatsoever in engineering which is why if confronted with a engineer trying to sneak a toolbox airside we insist on a letter of authorisation clearly stating just why he needs so many tools , people do not im sure realise what a danger tools can be airside, in the wrong hands they can pose a very serious security threat indeed which is why we are very alert to the dangers of engineers trying to blag there way airside with all manner of dangerous items.
However dont get me wrong, if the engineer is being sensible and has only one or two basic tools in his possesion, a torch and a pair of pliers for example that is not a problem, ...common sense has to prevail.