This is the final instalment of our rotary cutting series and looks at cutting the triangles needed for the Peaky and Spike unit.

The centre triangle is an isoceles triangle – its height and base are the same length, so you can cut it from a square. The triangles at the edges (long, or skinny triangles) are half as wide as their length and are thus cut from rectangles.

The square for the centre triangle should be cut 1 inch larger than the finished unit. If you want to cut more than one triangles then cut a strip 1 inch wider than the finished unit – for a 3 inch unit, cut a 4 inch strip.

Mark 4 inch squares along the length of the strip. Make sure you mark on the wrong side of the fabric as these marks may be visible later. The marks in the photos are heavy and thick so they show up, yours should be much lighter.

Once all the squares are marked you need to mark the midway points between the squares – in this example that would be at 2 inches.

These marks could be much shorter than the ‘square’ marks, or in a different colour.

Make the first cut by placing the ruler on the bottom of one ‘square’ mark and the next midway mark on the opposite side of the strip.

And cut along the edge of the ruler. No angles to measure here as isoceles triangles don’t have nice ‘easy to measure’ angles.

To cut the triangle place the ruler at the bottom of the next ‘square’ mark and at the tip of the cut you just made (on the midway mark).

and cut.

Cut the next triangle by placing the ruler at the base of the ‘square’ mark and the top of the next midway mark – (and you can see why you mark on the wrong side of the strip)

Continue along the strip until you have cut the number of triangles you need. Don’t forget that you can keep the strip folded and cut two triangles at a time – its much quicker.

Now its time for the skinny triangles. The rectangles should be 1 + 1/4 inches longer than the unit and 5/8 inch wider than half the width of the unit. So our 3 inch finished size units needs rectangles that are 4 + 1/4 inches x 3/2 + 5/8 (i.e. 2 +1/8) inches. For each unit you need two mirror image triangles – this means you need to cut two rectangles to start with. It is easier if you keep the strip folded and cut the rectangles in pairs.

Cut the paired rectangles in half across one diagonal.

This will give you two sets of mirror image triangles

These can then be paired with the larger triangles –

ready to stitch together.

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