Which type of outlet boxes may be used in electrical installations?

The correct answer is that octagonal or square boxes may be used in electrical installations because these box shapes are specifically designed to accommodate various electrical components such as switches, outlets, and junctions. Octagonal boxes are commonly used for lighting fixtures, while square boxes can be used for outlets and other devices. Their design provides ample space for wiring and allows for secure mounting of devices.

Furthermore, electrical codes and guidelines recognize a range of box shapes that ensure safety and functionality in electrical installations. While round and rectangular boxes are certainly utilized in certain contexts, octagonal and square boxes are more versatile and suited for a wider variety of applications.

The specification of excluding triangular boxes highlights that such shapes are generally not used for electrical installations due to practicality and compatibility concerns with devices and circuit layout requirements.