The physical set
A wooden stand holding ten pink-framed metal pieces. Each piece is a metal frame about 14cm square with a central metal inset in the shape of a specific figure: circle, square, equilateral triangle, rectangle, oval, ellipse, curvilinear triangle (a triangle with one curved side), trapezium, pentagon, quatrefoil.
Two pieces per shape are actually included: the frame (with a hole where the inset sits) and the inset itself (the central shape that can be lifted out). The child works with both: tracing inside the frame (the negative), and tracing around the inset (the positive).
A set of coloured pencils and small pieces of square paper (about 14cm square) complete the material. The paper usually lives in a tray alongside the insets.
What the work actually is
Two kinds, introduced in order.
Tracing. The child places the frame on a sheet of paper, picks up a coloured pencil, and carefully draws around the inside edge of the frame. They lift the frame. The paper now has the shape drawn on it. They then pick up the inset, place it inside the drawn outline, and draw around the outside of the inset. The two drawings should match.
The child repeats with a different coloured pencil, a different shape, a different paper. Over many sessions they develop the ability to move the pencil precisely along a metal edge without overshooting or wobbling.
Hatching. Once tracing is reliable, the child adds hatching: parallel lines drawn inside the shape to "fill" it. Starting with widely-spaced hatching and progressing over weeks to tightly-packed hatching. The hatching practises controlled, straight, parallel pencil movements within a bounded area.
The complete work for one shape is: trace the frame, trace the inset, hatch between the two lines, then sometimes colour the interior with different patterns. The resulting pieces of paper are often beautiful and often displayed.
The indirect aim: handwriting
The Metal Insets do not look like a writing material; they look like a drawing material. The indirect purpose is the motor skills writing requires: holding the pencil in the tripod grip (which the Knobbed Cylinder Blocks started at three), moving the pencil accurately along a line, controlling pressure so the line is neither faint nor heavy, starting and stopping where the child intends.
A child who has worked with the Metal Insets for a year can, when they come to form letters in pencil, reproduce the muscle movements that letter formation requires. The handwriting that comes out at five and six is noticeably more controlled than in children who go straight to letter-writing without the pencil-control preparation.
The Sandpaper Letters give the child the shape of each letter through the fingers. The Metal Insets give the child the pencil-control to form those shapes on paper. Together, the two materials cover the pre-writing foundation.
Progression through the year
Most home families introduce one shape at a time, over several months.
Month one. Circle and square. Tracing only. The child does a few papers per week.
Month two. Triangle and rectangle added. Still tracing only. The child is working across four shapes now.
Month three. Oval and ellipse added. Introduce widely-spaced hatching on the first four shapes.
Month four. Trapezium and pentagon added. Hatching becomes more consistent; the child is now covering the shape interiors.
Month five and six. Curvilinear triangle and quatrefoil added. Hatching progressively tighter. The child is now working across all ten shapes.
Month seven onwards. Extensions. Multiple shapes on one paper, overlapping. Hatching in varied directions. Hatching in different colours. Creative designs using the shapes.
Some children do all ten shapes in the first fortnight and get bored; others take a full year. The pace is the child's.
Common mistakes
Skipping the hatching. Tracing is the easy half; hatching is the motor-control work. A child who only traces has done half the material.
Correcting the tracing mid-stroke. If the pencil wobbles off the metal edge, the child notices. Adult correction of the line teaches the child that accuracy is someone else's judgement; the child's own eye should be the judge.
Using cheap metal insets where the edges are not smooth. Cheap sets have burrs or imprecise cuts; the pencil snags. Good sets are £35-70 in the UK; worth the money.
Using paper that is too big. A 14cm square paper fits the frame; a larger sheet leaves space around that the child is tempted to scribble on. Cut paper to match the frame.
Treating the material as decoration rather than daily work. The Metal Insets are a daily or near-daily material for the pre-writing year. A set used once a fortnight does not produce the motor development.
Extensions and creative use
Once all ten shapes are consolidated, the Metal Insets open into creative design work.
Overlapping shapes. Trace two or three shapes on the same paper, overlapping. Hatch each in a different colour. The result is a complex geometric design.
Pattern work. Trace the same shape multiple times across a paper, creating rows or tessellations. Hatch each one.
Letter and word pictures. Later, combine shapes to make representational designs (a house from a square and a triangle; a flower from multiple petals). The child is doing art within a geometric framework.
Colour theory exploration. Using the ten shapes as a framework for exploring colour combinations and contrasts. The Colour Tablets work informs this.
Many home families find the insets work evolves into a regular creative practice that continues past the pre-writing phase into art work at six and seven.
A real family's Metal Insets year
A mum we will call Nura introduced the Metal Insets to her son at four and two months, about four months after Sandpaper Letters began. She bought a set second-hand from a home-ed family for £45.
Month one: circle and square, tracing. Her son produced six or seven papers a week for several weeks, all circles and squares, all in different colours.
Months two to four: all ten shapes introduced progressively. Hatching added to the basic shapes. By month five his tracings were accurate and his hatching was showing the distinctive Metal Insets look of parallel fine lines across a geometric shape.
Months six to nine: extensions. He began overlapping shapes, sometimes using three or four shapes per paper. A whole wall of the hallway was papered with his Metal Insets work for a while; Nura has kept the best ones in a folder.
By month twelve his handwriting was noticeably more controlled than his older sister's had been at the same age (the older sister had not done Metal Insets). Nura attributes it to the inserts; she admits this is an n-of-two comparison and not science, but it matches the educator literature.