Drawing instructions
Right corner
By drawing along the rulers into the enclosed corner, two lines under an angle of 90 degrees occur.
Right corner triangle
When connecting the two endings of the previously created lines you will get a right corner triangle.
Diamond
For the centre position, use a pushpin. For high precision you might want to use four additional pushpins for the corners.
Place a first pushpin at the centre position of the diamond.
Place the enclosed corner of the rectangle hook against the pushpin in the desired orientation. Most logical is to have one ruler pointing left, the other ruler downwards.
Mark or place a pushpin at the desired horizontal ruler position for corner A.
Mark or place the third one along the vertical ruler for the B corner. Now the centre pushpin and the marks (or all three pushpins) are positioned in a triangle.
Lift the tool and rotate 90 degrees counter clockwise.
Place the enclosed corner of the tool again against the pushpin that marks the centre position and make sure the ruler touches the B pushpin.
Place a fourth pushpin for corner C, which is opposite A.
Rotate again 90 degrees.
Place a fifth pushpin for corner D in the identical ruler position as for corner B.
Connect the four corners.
Kite
In the kite shape the distance from ONE pair of opposing corners to the centre position differs. In other words, one of the diagonal lines is cut in two sections with different lengths.
Apart from this, the drawng instructions are similar as for the diamond.
Challenge
Fit a diamond exactly in the eight times six centimetres ellipse. The corners of the diamond are all four exactly on the ellipse outline.