Supermarket trolleys

[Carol Anne]

Does anyone know how they manage to lock if wheeled out of the car park?

[romko]

electromagnets i believe

[Buenchico]

Contrary to the suggestions above, the Radlok system is entirely mechanical:

See here:
http://www.gray-matter.co.uk/radlok.php
and (for more detail) the links from here:
http://www.gray-matter.co.uk/radlok4.php

Chris

[carlton23]

What a coincidence, I have just got back from Sainsbugs and as my wife and I were going back to our car, a womans well loaded trolley suddenly locked up in the middle of the car park and she was a long way from her vehicle. I couldn`t help her, being disabled and on a scooter, just in case anyone asks if I did.

[tamborine]

zap your hands and immobolise your muscles ;)

[New Judge]

It's the effect of spent dilithium crystals in the trolley coming into close contact with the green Kryptonite kept in the gatepost of the car park..