What do you do if a garage man announces that the car you thought was running fine actually needs hundreds of pounds spent on it?
Well, if you are like me, and filling the thing with petrol is the extent of your capabilities, you are aware it has an engine but that is as far as your mechanical knowledge goes, then you more or less have no choice but to bow to superior knowledge.
But what if he is robbing you blind?
You could take it to another garage for a second opinion, or you could ask a motoring assistance organisation to have a look. But that is all money and hassle.
Perhaps fittingly, I have discovered the professional version of the dodgy garage mechanic - the dodgy dentist.
Masked torturers, the modern day equivalent of the Spanish Inquisition.
Nevertheless, given dentists are mostly failed medics, I was always brought up to believe they were honourable men and women whose judgment you could trust.
Not so many of them these days, it seems - the base pursuit of money has turned some into greedy grease monkeys.
And I have the evidence. A pal of mine was getting fed up with his NHS dentist.
Not because of poor treatment, more to do with their lack of administration - appointment mix-ups and the like - coupled with the fact that he prefers to be examined sitting up. So he decided to take his business elsewhere - to a private dentist.
However in the midst of the changeover he got a problem and in some degree of discomfort asked and got an emergency appointment with his original practice.
The only thing wrong with him, they said, was a small filling. Dubious, our man decided on a second opinion at the posh, new private dentistry centre.
He was told his teeth were an absolute disaster, he would need at least five crowns plus a whole load of other work, and it would cost him more than £3,000.
Naturally - when it is not you in pain you can delight in pontificating - myself and some of his other chums had plenty of advice.
We decided he should go down the dental hospital in the centre of Birmingham and get himself an independent assessment.
No, they really weren't all apprentice butchers, we assured him. But he looked at us warily and you could tell he was not convinced. Neither was he going along.
I bumped into him the other day and inquired as to his predicament.
He had indeed decided on a third opinion - off one of the top private dentists he could find.
And this man sided with the first one - all that was needed was a single filling, albeit it wasn't the same bit of tooth.
So he is a relieved man . . . but it begs the question.
Just like the dodgy garage mechanic, they can tell you any old rubbish, ratchet up the bill, and the poor bloke in the chair, lying back and praying to God for salvation, is none the wiser.
Of course these days you are jolly lucky to get an NHS dentist - often any dentist - to take you on.
No wonder if this is what the industry gets up to.