Companies are telling prospective recruits - especially among the low- paid and unskilled - that when they turn up for work, they won't necessarily be paid. In the case of the Burger King in Glasgow, the young man would be made to clock on when the restaurant was busy and clock off again when it was quiet. Many thousands of employees now work under such circumstances.
It is all part of a trend whereby employers are resorting to a wide range of imaginative techniques for squeezing work out of the low-paid in return for the smallest possible reward. With increasingly fierce competition and little scope for pushing up prices, companies - especially in the service sector - are maximising profits by minimising wages and introducing inferior conditions.
The "casualisation" of the workforce - in which secure full-time employment is being replaced by temporary terms or freelance employment - and the gradual erosion of collective bargaining have helped employers to drive down labour costs.
Companies have been increasingly keen to match the number of employees at the workplace at any one time to the amount of work available. Three years ago, the Burton menswear group offered many of its full-time staff the option of severance or new contracts of employment which only held out the possibility of part-time work at peak periods.
Another device is the introduction of "split shifts", in which employees can be called upon to work two shifts a day with a long gap between. Restaurant staff might be required to work from 11am to 3pm and then from 6pm to 10pm.
Increasingly employers, particularly in the building industry, will offer work on the basis that new recruit is "self-employed", even though the person concerned has only one employer and is paid an hourly rate. Such a status gives the worker the impression that he or she has no employment rights. Many are too frightened of losing their jobs or unaware of their rights to challenge their designation.
Even where contracts have been issued, some of the worst employers will unilaterally change the terms. Workers have found that companies have stopped or minimised holiday entitlement, changed working hours or cut wages - or all three.
Some contracts are only signed by the most desperate. The "zero hours contract" is perhaps the worst, but its use is burgeoning, according to the National Association of Citizens' Advice Bureaux.
Technology is also helping employers to keep an ever tighter control of their employees' productivity. The number of "keystrokes" per minute in typing pools is monitored by most large companies on a daily basis. At the big retail stores, management will know at any time of the day how much merchandise has been processed by a particular checkout operator. Staff are sometimes threatened with dismissal or demotion if they cannot keep up the required rate. The most exploitative employers, however, are small firms where paperwork of any kind is kept to a minimum and pay is strictly in cash.