Our grandmothers used whatever they could find to make templates. Lightweight cardboard was the most commonly used material. Quilters today still use cardboard from many sources including cereal boxes, pieces found in new shirts, empty tissue boxes, etc.
Cardboard templates work well for a short time, but after use the edges wear and distort, making accuracy impossible. Plastic templates solve the distortion problem. Many varieties of plastic template material may be purchased - with or without graphed lines; rough on one side, smooth on the other; clear or opaque; non-melting for pressing appliqué shapes; large sheets and small page-size pieces.
Some quilters recycle plastic milk cartons, old X-ray film and other plastic items.
Precut plastic see-through templates are available for many popular patterns. They are extremely accurate and will never wear out, but unless you like a particular pattern and want to duplicate it many times, you may not want to invest in such a template set.
Whether you make homemade templates from recycled plastic or cardboard, or purchase pre-made sets, each template should be accurate and marked with the pattern name and piece number or letter to identify it.