Golden triangle (composition)
The golden triangle is a rule of thumb in visual composition of photographs, paintings, and other visual art—especially those that contain elements with diagonal lines. The rule visualizes the frame divided into four triangles of two different sizes, by drawing one diagonal from one corner to another, and then two lines from the other corners, touching the first at 90-degree angles.
Source: Wikipedia — Golden triangle (composition) (CC BY-SA 4.0)