Same shape and same size: superimposition as the test

What to assume they know

Measuring a length in centimetres with a ruler, and an angle in degrees with a protractor
Naming the corners of a figure with capital letters, and reading ∠ABC as the angle at B
The four angles at a crossing: vertically opposite and linear pairs — angles at a crossing, and the habit of arguing about a figure from its labels rather than from its picture
Drawing a circle of a stated radius about a stated centre
The idea, from Class 6, that turning or flipping a shape does not change the shape

What they should be able to do

State what has to be true of two figures for them to be congruent
Use superimposition — including a turn or a flip — as a test on two drawn figures
Explain why tracing is a poor method for transmitting a large shape
Show, from the book's own four-symbol picture, that two arm lengths do not determine a two-armed figure
Say which third measurement removes the ambiguity, and why
Decide, for a circle and for a rectangle, how few measurements are enough
Predict how the list of needed measurements grows for a figure with three arms
Distinguish "these look alike" from "these are congruent"

Where it usually goes wrong

"Congruent means the same shape." Half the definition. The four symbols on p.2 are all the same kind of figure built from the same two lengths and are not congruent; the three triangles on p.10 have identical angles and are not congruent either. Size has to agree too, and this chapter says so in the same breath both times.
"If it has been turned round, it is a different figure." The chapter puts the turned and flipped pairs on pp.2–3 precisely to close this off. Congruence is judged after you are allowed to move the tracing.
"Two figures that look alike are congruent." Figure it Out question 2 asks which pairs appear congruent — a careful choice of word. Looking alike starts the investigation; superimposing or measuring finishes it.
"More measurements are always safer." The chapter is pushing the other way: it wants the shortest sufficient list. A circle needs one number. Saying "and also its area, and also its circumference" adds nothing and hides what is doing the work.
"A figure with three arms must have them evenly spread." The figure printed on p.4 is drawn lopsided on purpose. Nothing in the chapter forces equal spacing, and an explanation that tidies the picture teaches a rule the book is refusing to state.
"Congruent and equal are the same word." Two figures are congruent; two lengths are equal. The chapter keeps the two words apart from the start, and the ≅ sign it introduces in Part II, §1.2 is not the = sign.

Questions to check understanding

Given two drawn figures, state whether they are congruent and say what test you applied
State the minimum measurements needed to reproduce a named shape (circle, rectangle, two-armed symbol)
Given two circles with stated radii, or two rectangles with stated sides, decide whether they are congruent and justify it
Produce a counterexample: two non-congruent figures that agree on a stated incomplete list of measurements
Explain why a turn or a flip is permitted when testing congruence
Divide a given region into a stated number of congruent parts
Items of this shape appear right through the chapter's four "Figure it Out" blocks and are compressed into the first two bullets of the SUMMARY (Part II, p.22)

Examples worth working on the board

The signboard symbol (Part II, §1.1, p.1). Checked against the printed page. A roadside board carrying a hand-drawn tick. Below it the same two-stroke figure is redrawn bare and lettered: A at upper left, B at the bottom, C at upper right, with strokes A–B and B–C. That is the whole figure — two segments meeting at B.
The two arm lengths (Part II, §1.1, pp.1–2). Inputs: AB = 4 cm, BC = 8 cm. Do not draw a conclusion from them; the point of the passage is that they are not enough.
The four-symbol row (Part II, §1.1, p.2). Checked against the printed page. Four two-armed figures printed side by side, every one lettered A, B, C, every one built from the same two lengths, and every one bent by a visibly different amount at B. Measured off the printed page, the angles at B run roughly 86°, 70°, 48° and 96° from left to right — so they do not widen steadily: the third is the tightest of the four and the fourth then opens widest. Say it that way round, because "they open progressively" is the natural thing to assume from a row of four and it is not what is printed. This picture is the argument; give it attention.
The closing measurement (Part II, §1.1, p.2). Input: ∠ABC = 80°. With AB = 4 cm, BC = 8 cm and this angle, the copyist has no choice left.
Two congruent figures to superimpose (Part II, §1.1, p.2). Checked against the printed page. Two pairs sit on this page: a rounded eight-sided pink tile beside a turned copy of itself, and a circle with a square notch cut out of one quadrant beside a copy of that. The reader is told to trace the first and lay it on the second.
Turned and flipped pairs (Part II, §1.1, pp.2–3). Checked against the printed page. Two further pairs straddle the page break: a thick L-shaped bracket beside the same bracket rotated a half turn, and a disc split down the middle with the two halves shown facing opposite ways. These are the pairs that make "rotate or flip first" concrete.
Figure it Out, question 2 (Part II, §1.1, p.3). Checked against the printed page. Four pairs to be judged by eye: two teardrops, two clouds, two starbursts, two leaves. Only some pairs match; the exercise is deliberately about appearing congruent before any measurement is taken.
Figure it Out, question 3 (Part II, §1.1, pp.3–4). Two shapes are named — a circle and a rectangle — and the reader is asked what to measure to reproduce each, and then how to test two given ones. One number for the circle, two for the rectangle.
Figure it Out, question 4 (Part II, §1.1, p.4). Checked against the printed page. A figure with three arms leaving a common point — and the three arms are deliberately not evenly spaced: two of them run almost straight through the junction, so that much of the figure reads as one long stroke, and the third branches off it at roughly a right angle. Two further pairs of such figures follow, to be judged congruent or not. Redraw it that way. Straightening it into a neat three-way star destroys the reason it was printed.
The closing puzzle (Part II, "Expression Engineer!", p.23). Checked against the printed page. A 5 × 5 grid of squares with the single centre square shaded green. Twenty-four white squares remain, to be split by drawn lines into six congruent regions — so four squares to a region. The 24, the 6 and the 4 are the inputs.

Figures to have open

The two-armed lettered symbol, redrawn, with A upper left, B at the bottom vertex and C upper right, and the arms labellable with lengths and the angle at B. Standard schematic; it must be re-drawable at four different openings for section 4.
Two congruent shapes that are visibly not in the same orientation, so that the turn-and-flip step is needed. Standard schematic — do not lift the book's own tile, bracket or split-disc artwork.
The lopsided three-armed figure of p.4. Redraw it, keeping the uneven spacing; this one is load-bearing.
A 5 × 5 grid with the centre cell shaded, for section 11.
No photograph or data table from the textbook is needed for this topic.

Where this sits in the book

NCERT Ganita Prakash, Class 7, Part II, printed Chapter 1 "Geometric Twins", §1.1 "Geometric Twins", pp.1–4 — the signboard and the lettered symbol (p.1), the four same-length symbols and the naming of congruent (p.2), the turned and flipped pairs and the return to the two signboards (pp.2–3), and the first "Figure it Out" block (pp.3–4)
Same part, same chapter, SUMMARY, p.22, bullets 1 and 2
Same part, same chapter, "It's Puzzle Time! — Expression Engineer!", p.23
Forward pointer: SSS: three sidelengths fix a triangle completely, where the same "which measurements are enough" question is asked about triangles