Ask anyone to conjure up an image of a painter’s canvas and chances are they’ll picture a rectangular one. The rectangle’s dominance is as much a technical matter as an aesthetic one—canvas is easiest to stretch on a squared-off frame. But something as simple as changing the shape of a canvas can have an enormous impact on the work. Many attribute the advent of the shaped canvas to the turn-of-the-century Constructivist movement and artists like Peter Laszlo Peri, who challenged the conventional idea of painting and mounting surfaces, but simple shapes like the Florentine tondo, a circle, were popular long before that. In the mid 20th century, a period of great experimentation, many artists tried the transformative power of the shaped canvas. Whatever your style, finding a good, taut canvas is essential. Below are five recommendations that will have you covered.