How-to
A step says what to achieve and a build says how to make one object. Neither covers "how to fish", which is a set of techniques, a body of identification knowledge, and a list of things that will kill you. That is what a field guide is for.
Water & Sanitation
The thing that kills first, and the one problem on this site that is completely solved — provided you do it every single day, including the day everyone is exhausted.
Serves 4 steps · Make water safe
The distance between a latrine and a well, a bar of soap, and a covered pit prevent more deaths than every hospital on the ladder combined.
Serves 5 steps · Sanitation
Surface water is a treatment problem every single day. Groundwater, reached and sealed properly, is a treatment problem once.
Serves 3 steps · Find and store water
Water in and on the ground, the air and weather, rocks and time, earthquakes and tsunamis, and the climate: each result with what it lets you do and who first found it.
Serves 9 steps · Find and store water
Food & Agriculture
The highest calorie-return food source available to a group with nothing — and the one most often worked in the least productive way.
Serves 3 steps · Wild food
Wild plants and fungi are mostly water, fibre and vitamins. A handful of them are food worth carrying home, a handful will kill you in a way no taste, smell or cooking can warn you about, and the difference is knowledge you hold before you pick.
Serves 1 step · Wild food
A glut eaten in the week it arrives is a feast. The same glut dried, salted, fermented or cellared is the difference between March and a famine.
Serves 4 steps · Storage and preservation
Animals turn grass nobody can eat into milk, meat, wool, leather, manure and traction. They also turn raw milk, a birthing ewe and a dog fed on offal into diseases that kill people.
Serves 4 steps · Livestock
What a soil is made of, why its acidity matters, and how to read a nutrient shortage in the leaves before it costs a harvest.
Serves 5 steps · Crops and soil
A trapline works all night while you sleep. A hunt works only while you are awake, usually returns nothing, and burns the calories it was supposed to find.
Serves 4 steps · Wild food
A seed is a living embryo with a shelf life. Kept dry and cold it waits for years; kept warm and damp it dies in a season — and the difference is two rules of thumb and a sealed jar.
Serves 4 steps · Crops and soil
Keep the soil covered, feed it, water the roots and fight pests without poisoning yourself: the modern practice that needs knowledge rather than machinery.
Serves 7 steps · Crops and soil
What a greenhouse is for, which kind to build, its parts and how to size them, and how to run its climate: from a cold frame over manure to a heated glasshouse and a solar greenhouse that needs no fuel.
Serves 4 steps · Protected growing
A drainable earthen pond, manured from the farm's animals, grows fish without bought feed: site, species, water, stocking, feeding, daily care and harvest.
Serves 1 step · Aquaculture
Shelter & Architecture
Density, stiffness, expansion and melting point for the materials the ladder makes, and what each number decides.
Serves 7 steps · Building materials
How to build a dwelling that stays dry and standing for thirty years from subsoil, stone and timber: choosing the method, setting out, foundations, walls, roof, drainage, and how to inspect, repair and maintain it.
Serves 7 steps · Dwellings
Settlements & Planning
Health & Medicine
Without antibiotics, a cut is a slow emergency and a deep bite is a fast one. What saves people is mostly pressure, water, and knowing which wounds must be left open.
Serves 3 steps · First aid and surgery
The two dozen that decide who lives where there is no doctor: what each does, how it spreads, what kills it and which step stops it.
Serves 11 steps · Hygiene and disease
The basic set from the WHO list: what each treats, what it is made from, and the earliest tier that can make it. No doses, on purpose.
Serves 7 steps · Medicines
Normal pulse, breathing, temperature and blood pressure; the signs that mean danger in a child; and how much water a body needs.
Serves 4 steps · First aid and surgery
The poisonings a rebuilding community is most likely to meet: where each comes from, how it shows, and the first thing to do.
Serves 8 steps · First aid and surgery
Life from the cell up: the human body, microbes and immunity, inheritance and epidemics. Each result with what it lets you do and who first found it.
Serves 11 steps · First aid and surgery
Energy
Making fire once is a trick. Never having to make it from nothing again is the skill, and the difference between them is tinder you collected yesterday.
Serves 3 steps · Fire and fuel
Throw away two-thirds of the energy in a pile of wood and what is left is the only fuel that reaches the temperature of molten iron.
Serves 3 steps · Fire and fuel
Not a source of energy but a way of carrying it: make it, move it, store it — and know exactly how it kills.
Serves 5 steps · Electricity
Every source of energy in one place: what it gives, what it takes, and how it can hurt you. Key figures, a reference sheet for each, and where to read further.
Serves 9 steps · Electricity
Materials & Chemistry
Burn a rock, add water, and it turns back into rock in the shape you gave it. Mortar, plaster, whitewash, soap and tanning all start there — and so does an alkali burn that can blind in seconds.
Serves 3 steps · Binders
Fired clay is the first material a group makes that does not exist in nature: a rock with a shape you chose. Getting there is mostly patience — in the drying, and in the heating.
Serves 2 steps · Ceramics and glass
How to tell the ores that matter with nothing but a streak plate, a knife and your hand: colour lies, streak and weight do not.
Serves 5 steps · Metals
A dozen knots cover almost everything. Two of the most familiar ones — the reef knot and the granny — have killed people who used them for the one job they cannot do.
Serves 3 steps · Fibres, textiles and leather
Cloth is a chain of slow jobs — growing, retting, spinning, weaving, finishing — and for all of history the slowest link was spinning. A weaver needed several spinners working full time to keep one loom supplied.
Serves 3 steps · Fibres, textiles and leather
What matter is made of and how it changes: amounts, gases, acids, the energy and speed of reactions, electrochemistry, and the reactions every industry on the ladder runs on.
Serves 12 steps · Chemicals
Tools & Industry
The forest is the first material store, the first fuel supply and the first thing a group kills itself cutting down. Managed, it is also the only one of the three that grows back.
Serves 5 steps · Woodworking
Iron is shaped by colour. Read the heat right and a bar of scrap becomes a chisel that holds an edge; read it wrong and it cracks, burns, or stays as soft as a nail.
Serves 4 steps · Metalworking
Turning the sciences into things that work: machines, structures, water in pipes and channels, heat through walls, and feedback control. Each result with what it lets you do and who first found it.
Serves 11 steps · Production
Transport
North is written in the sky twice a day and all night. Latitude is one angle measured at noon. Everything else is counting paces and not lying to yourself about the count.
Serves 4 steps · On water
Which boat to build from what you have, how much it carries before it swamps, what keeps it upright, and the rules that keep its crew alive: from a log raft to a fibreglass skiff.
Serves 6 steps · On water
How a surface in moving air makes lift, how much a balloon carries, how kites and models are balanced, and why every flying machine is tested without a person in it first.
Serves 6 steps · In the air
Knowledge & Education
Fourteen branches, each with the handful of results a civilization cannot rebuild without, and where to learn the rest.
Serves 13 steps · Science and measurement
Four-figure logarithms and trigonometry, square roots by Newton's method, and the two instruments that did the world's arithmetic before electronics.
Serves 4 steps · Teaching
The results every other science and machine is built on, in the order each needs the last: the formula, what it states, what it lets you do, and who first found it.
Serves 6 steps · Teaching
Force, energy, heat, light, electricity, relativity and the atom: the laws every engine, wire and lens obeys, each with what it lets you do and who first found it.
Serves 9 steps · Science and measurement
The sky as calendar, clock and compass, then orbits, distances and the universe: each result with what it lets you do and who first found it.
Serves 5 steps · Science and measurement
Communication & Computing
Radio, heat, light, ultraviolet and X-rays are one thing at different wavelengths: what each band does, and the radio bands by name.
Serves 4 steps · Signals
What can be computed and how fast, how signals carry information without error, how secrets are kept, and how machines learn from data: each result with what it lets you do and who first found it.
Serves 6 steps · Electronics and computing
From a relay to a stored-program computer: what makes a switch compute, diodes and transistors, logic, memory, the processor, and how chips are made, each with the numbers that decide it.
Serves 5 steps · Electronics and computing