Probably the two most important factors underground are survival and movement: if you didn't survive you wouldn't be around long enough to do much moving, and if you didn't know how to move you wouldn't survive very long. Even a complete idiot could survive underground given light, food and warm clothing; indeed, many do. But give that same idiot several hundred feet of tackle and turn him loose in a really vicious pothole and the probability is that, unfamiliar as he is with the tackle, he will probably kill himself; again, it is an unfortunate fact that many do. The moral is obvious: tackle alone is not enough - if you don't know the technique you are going to die.

So, SURVIVAL: I'll deal with this first, since it calls less for technique than for good equipment. No, this isn't going to be yet another lecture on what to do when the flood-water is up to your neck and you're running out of hymns and Mars Bars - you're unlikely to get into that sort of situation anyway, and if you do it's probably your own fault. In fact this section is about tedious little things like keeping warm and not wearing your knees out in crawls.

Wet-suits: nobody really likes them except cave-divers and people who've just forked out £15 for a super-deluxe status-symbol. They're expensive, uncomfortable, need a lot of upkeep, wear you out on ladders and restrict your ease of movement. And if you doubt this and have worn one ever since your first trip down Goatchurch, go down a nice dry cave in sweater and jeans and see how much easier it is. What you do lose is the advantage of padded elbows and knees, but there are other ways of protecting them: ex-NCB kneepads, for example (though preferably not too 'ex').

What possible replacements are there then for wet-suits? The hardest club in France, the Spéléo-Club de la Tronche, have special under-boilersuits made for them in a fantastic material called Rexotherm; this consists of a Space-Blanket type super-insulation metal foil, pierced with thousands of tiny holes for aeration and sandwiched between two layers of lightweight nylon. The suit, which is extremely light, has elasticated waist and cuffs and is normally worn under a protective outer layer. It is said to be as warm as four layers of Long Johns.

This same club also makes its own boilersuits out of nylon painted with rubber solution. There is another possible use for this technique; one-piece Long Johns, made of wool, Rhovyl or Thermawear, coated with rubber. They would work in the same way as wet-suits but would be considerably cheaper and more comfortable.

Either of these articles would be worn under a boiler-suit of some sort. The shortcomings of the conventional cotton ones are well-known and commercial nylon ones, although much lighter, more comfortable and less water-retentive, are rather flimsy. A good design for a simple homemade heavyweight nylon boilersuit is given in the Journal of the Wessex Cave Club, no. 130 Vol. II; one problem seems to be finding a suitable material. How about terylene sailcloth? It is easily obtainable at any ship's chandlers and many sailmaker have large scraps left over which they are only too glad to get rid of.

A useful compromise for a really wet cave is a shorty wetsuit in combination with a heavy boiler-suit and, maybe, a Rexotherm under-suit. It keeps your trunk warm and doesn't tire you on ladders. And if your legs still get cold, try a pair of women's woollen ski-ing tights. If you can summon up the courage to ask for them in the first place, you will easily be able to shrug off the hoots and jeers when you change into them in your local caving hut!

For some reason the subject of gloves always stirs up a lot of controversy. If you wore them at all, they used to be heavy cotton or leather gardening gloves, which got soaked in no time. Then came the thin rubber ones which lasted one trip before they were riddled with holes. The answer now seems to be thick semi-industrial rubber gloves, which are lined, wear well, retain warmth and are sufficiently sensitive for all but the hardest climbs. 'Northands Glovelies', available from Boots, are a good example.

MOVEMENT: for moving along easy horizontal passages you can't really improve on walking. Likewise, it has been shown by extensive tests that swimming and crawling are ideally suited to canals and low passages. Come to think of it there isn't much scope for refinement of technique anywhere but on pitches. Which is why I propose to deal here only with pitch techniques. And the only techniques which have really become common recently are abseiling and brake-blocking. Prusiking is not all that important since there are relatively few pitches in Britain where it can be used.

In a way it is a pity that abseiling is so easy, because it is also potentially very dangerous. Many cavers are so dazzled by its increased speed and simplicity that they ignore the greatly reduced safety-factor. There are many "don'ts" in abseiling: DON'T use the classical method on any but very short pitches; it is inherently unstable and if the rope comes off your shoulder you're a 'goner'. Similarly, DON'T use the krab abseil; again, you'll fall if the rope comes off your shoulder. DON'T use the P.A. 'toasting-fork' descendeur, which is absolutely lethal; as well as being very fragile, the rope can come out of it easily. DON'T use any of those clever linked-krab or brake-bar devices (such as the Magnone); they depend on positive control by the user and are too complex.

In fact the only really safe descendeurs currently available are the 'roulette' and the 'figure-of-eight'. The roulette, which resembles a double pulley-block with fixed sheaves, was designed in France specifically for caving. It gives excellent control with no twisting of the rope. Two slight disadvantages: it gets rather hot on big, dry pitches (this can be overcome either by wetting the rope or by using only nylon - Ulstron has an uncomfortably low melting temperature), and it was designed for use with 11mm kernmantel rope, the diameter of which is slightly less than no. 4 nylon. Accordingly it can be slow and juddery at times. Mountaineers recommend that kernmantel only be used 50 times or for two years, so it is obviously unsuitable for a much more destructive sport; the answer is to use no. 3 nylon if necessary, although this does call for more control.

The figure-of-eight is available in several different sizes and shapes. Those who never felt happy on those little bits of coathanger wire which used to be sold as descendeurs and which made such frightening noises when you used them, will be pleased to know that that particular design has been withdrawn. The best now available is the Clog; its only real drawbacks are its size (although it is very light) and the fact that it tends to twist the rope on big pitches, although not so badly as the little ones used to.

Their use is fairly straightforward. It is important not to jerk too much, but to descend as smoothly as possible. Also, if you slide down pitches too fast you are likely to catch and break your ankle in a crack. I heard somewhere (I don't know if the figure is correct) that 90% of all abseiling accidents in climbing are caused by faulty belays. It is absolutely essential that the belay-point be safe. If a ladder breaks you should, in theory, be held by your lifeliner. In abseiling you don't have a second chance. Use a double belay wherever possible.

It is very uncomfortable (but amusing to spectators) to abseil with a descendeur fastened directly to your waistlength: an ordinary leg-loop will do, but it gets a bit tiring putting it on and taking it off all the time. Half an hour's Heath-Robinsonry with bits of nylon tape is enough to make a comfortable sit-sling which will double as a NiFe-belt (see Descent 19).

It is only logical to progress from abseiling to brake-blocking. Readers who are unfamiliar with the technique of self-lining are recommended to read the article in Descent no. 10 by Dave Everett. Suffice it to say that a brake-block is a form of jam-cleat which will run one way only on a rope; the rope is fastened at the top and tensioned at the bottom and the climber clips his block, which is krabbed onto his waist-length, onto the rope. There is very little friction and no disconcerting pull. This form of lifelining, however, does have considerable disadvantages for inexperienced cavers. In the first place, no help can be given to the first man up, should he need it. Subsequent climbers can of course be hauled up in the usual way. Secondly, there is the very difficult problem of what to do if the ladder breaks or swings away. In fact there is a solution, but it is very energetic and calls for considerable presence of mind.

Imagine yourself hanging in mid-air by your brake-block. Assuming you have no prusiking gear there is only one way to go - down. It is essential to have a descendeur and a spare krab. Put the descendeur on the slack rope immediately below the block and krab onto it. Wind the rope a few times round one of your boots several feet down (only experience will tell you how far) and stand in it, taking your weight off the brake-block. Unkrab from the block, unwind the loop and lock the descendeur. Remove the block, free the descendeur and abseil down. On the first attempt you will reach the ground after ten minutes or so, a quivering nervous wreck. Now imagine doing this on a 200 footer with a waterfall pounding on your head!

It is this inherent danger in brake-blocks that makes them unsatisfactory. However, there can be no denying that in the hands of competant cavers they can speed up a trip enormously. We realise their shortcomings at Cambridge and are currently working on a device which will double as brake-block and descendeur.

Brake-blocks can also be used for prusiking, where necessary, and they are very useful indeed for ordinary toplining. One word of warning about combining the techniques of abseiling and self-lining. When a pot is to be rigged without DLs it is quite easy to abseil to the bottom effortlessly and to underestimate the severity of the return trip. Far better to play safe.

NICK RECKERT