Tinkertoy

Pajeau claims a spool with a centre hole and a ring of rim holes at equal angles, joined by rods, so structures can be built in any direction. Note: the fixed hole angles are the whole idea.

Cut a short thick disc (a spool) from a fat dowel or plywood. This is the hub every rod will plug into.

With a protractor, mark eight points 45° apart around the rim, plus one through the centre, and pierce a hole at each. Equal angles are what make the geometry repeatable.

Cut several rods from thin dowel, sized to push snugly into the spool holes. Make a few lengths.

Push rods into the rim holes. They stick out as spokes at exact 45° steps — a wheel of arms from one spool. No angle guessing.

Connect two spools with a rod between them. You can now extend in a straight line — spool, rod, spool, rod — as far as you like.

Make a square from four spools and four rods and push a corner. It racks — like any four-bar frame, it has no stiffness yet.

Use a rim hole to plug a diagonal rod across the square. Now it is rigid — the fixed 45° holes gave you the diagonal exactly where you needed it.

Add rods straight up from the corner spools and cap them with more spools. The structure leaves the table and becomes a cube or tower — building in three dimensions from two parts.

Fit a rod loosely through a spool's centre hole so it spins, and build a windmill or wheel on it. The centre hole gives you an axle; the rim holes give you spokes.

Pull the rods out and build a bridge, a crane, a person. Because nothing is glued, the same handful of parts becomes anything — the point of the system.

Write it down: a hub with angled holes plus plain rods is enough to build almost any framework. Constraint (fixed angles) is what makes free building possible and repeatable.

The patent. US 1,113,371, "Toy Construction-Blocks", granted 13 October 1914 to Charles H. Pajeau of Evanston, Illinois. (It is often misdated to 1917 — the grant is 1914.) Pajeau, a monument-maker, reportedly watched children endlessly poking pencils and sticks into empty wooden thread spools and turned that play into a system: a spool drilled with a centre hole and eight rim holes, plus rods, sold from 1914 in the famous cardboard canister. It was an immediate hit after he demonstrated it in shop windows at Christmas.

The idea is a connector that fixes the angles for you. Two loose sticks meet at whatever angle your hands hold; to build a repeatable structure you need joints at known angles. Pajeau's spool encodes the angles in the holes: eight rim holes 45° apart mean every rod you plug in points in an exact, predictable direction, and the centre hole gives you an axle for anything that must turn (steps 5, 10). With only two kinds of part — the angled hub and the plain rod — you can make spokes, squares, triangles, cubes, wheels and towers, and (as with the Erector Set's strips) a diagonal turns a floppy square into a rigid triangle (steps 7-8). It is a beautiful lesson that constraint enables freedom: by fixing the angles, the system lets you build almost anything, quickly and repeatably.

Where it sits. Tinkertoy, Erector and Meccano, and later LEGO Technic, are all the same insight — a small kit of standard parts with standard connections, from which endless machines and structures follow. Engineers call this modularity, and it is how everything from scaffolding to electronic connectors to software is built. The wooden spool you drilled, with its ring of angled holes, is one of the purest toys ever made: almost nothing, from which almost anything.