The French curve is a template used to draw different types of curve. It is called a cloud template in Japanese because of its resemblance to a cloud. The French curve enables the artist to draw curves that would be difficult to achieve with a compass. It is normally sold in a set of multiple templates and can, therefore, be used to achieve a wide range of curves. The user searches through the templates for the desired curve. French curves are made of acrylic, transparent plastic and even wood. There are also universal French curve templates with multiple curves on a single template. These take the place of multiple templates and enable the work to be done with fewer templates. Universal French curves are usually 12cm to 21cm in size.

A rough outline of the desired curve is first drawn, the template is then placed against that and a line drawn around it. French curves have lots of curve templates but that does not mean that the complete line can be drawn with just one curve. This can be done by dividing a single curve into several parts and selecting the right template for each part. When connecting the lines, take care to ensure that they join smoothly.

In addition to the French curve, flexible rulers can also be used to draw arbitrary curves. These are PVC tubes with a metal core and can be flexed into the desired curve. However, they can be difficult to use for small curves. Flexible rulers come in various sizes ranging from 30cm to 80cm, some with gradations and some without. Other templates for drawing curves are uni-curve rulers which come in a set of five templates for drawing ellipses, spirals and other geometric shapes. Specialist types include railway curve rulers. Some railway curve rulers come in a set of as many as 100 templates for subtle differences in the curve. French curves, uni-curve rulers and other templates for drawing curved lines can be purchased at art supply stores and shops selling drafting tools.