Willie-o - I've always hear that one with it being an Irish lad who helpfully sorts it out. "I think I see your problem" ,and he reaches his hand out and moves the obstruction out of the way as the blade comes down.

What I find interest here is that the same joke here plays with different national stereotypes, but sympathetically in both cases.

With it being a Scot the stereotypoe is of a Scottish Engineer - a man with an irresistable urge to sort out the mechanics of things that are broken; with it being an Irishman it's of a man who is helpful and ingenious, but is prone to not keeping all the aspects of the situation in his head at the same time. (And I recognise myself in that.)