OVER THE years, builders have come up with many ideas for deterring intruders. One of the most cunning was the false step, where one riser in a staircase was built an inch higher than the others, so that anyone unused to those particular stairs would trip up and make a racket. Note the staircase terminology here - rise is the height of a step and going is its depth. The names of the actual timber components are riser and tread. Got that? Good, I'll be asking questions later.

Anyway, the idea of the false step is a good one, because once you get walking up or down stairs your legs quickly go into auto-pilot mode, and trot happily along, confidently expecting each step to have the same rise and going as the last, while the upper parts of your body forget about all that and go back to thinking about sex or food or work, or whatever else it is that lies in wait at the end of the staircase. So if there is one step different from the others you fall over. Just like that.

Modern building regulations naturally require uniformity of rise and going, so the only false-step situation that most people encounter is where the original ground-floor level has been raised by adding a new tiled or timber surface on top of the old one, thus reducing the rise of the bottom step by around an inch. This always gets you as you come running happily downstairs to rejoin the party - the fact that the floor is an inch nearer than it should be can be even more of a shock than when it is an inch further away, and the jolt can sometimes cause quite serious leg or spine injuries. Funny thing is, when you live with that sort of staircase you get used to it remarkably quickly - and then you injure yourself on other people's stairs that don't have the false step.

These days, burglar deterrents are nothing like as subtle. Most people's security precautions begin and end with a 500 watt halogen floodlight aimed straight into the eyes of anyone having the temerity to approach the front door. These ghastly devices are switched on by passive infra- red (PIR) detectors that are supposed to respond to human body warmth but are in many cases triggered by passing cars, cats, slugs or even waving vegetation. The sensitivity of the triggering and the length of time the light stays on can be adjusted, but this is rarely done. The popularity of these KGB-inspired searchlights is largely due to their current cheapness - less than pounds 20 - but for the same money you can buy a PIR switch on its own and wire it into a more attractive lighting system, such as wall-mounted lanterns or garden lights spiked into the flower beds. Experiment with the angle of the switch so that it is not activated by passing cars or pedestrians.

You could even arrange for the lights inside the house to come on when someone approaches the front door - make sure the staircase stays in darkness, though; if it is a burglar then you don't want him to be able to negotiate your false step, do you?

`Struck Off - The First Year of Doctor on the House', by Jeff Howell is available from Nosecone Publications, PO Box 24650, London E9 7XQ, price pounds 9 inc postage.