Samir & Aly French Curve Set, Clear Plastic, 3 Pieces, Boxed

A French curve is a template of smooth, continuously changing curves — no arc on it is a plain circle. You use it to draw a fair curve through points a compass cannot join: the sweep of a car body, a cam profile, a graph line, the line of a hip on a dress pattern. You find the part of the edge that fits your points and trace along it.

A set of three covers the range — you match the tightest usable radius on any of the three to the section you are drawing, then move to the next section and often the next curve. Clear plastic lets you see the points underneath as you align it. Keep ink off the drawing edge, or wipe it at once, because dried ink on the bevel is what makes a French curve trace a dirty line ever after.

The same three-piece set supplied boxed. For a set of drawing tools the box is genuine protection rather than packaging — a French curve with a chipped or scratched edge traces that flaw into every line, so a case that keeps the edges true is worth having if the set travels or shares a drawer with harder tools.

• Set of 3 clear plastic French curves
• Draws fair curves a compass cannot make
• Clear plastic — see the points as you align
• Keep ink off the edge, or wipe it at once