314.2 Electrical Boxes and Fittings(A) Installation. In completed electrical installations, each outlet box, junction box, and fitting shall be securely fastened in place.(B) Concealed Work. In concealed work, each outlet box, junction box, or fitting shall be installed in such a manner that the center of the box or fitting will be within 1/4 in. (6.4 mm) of the finished surface.(C) Exposed Work. In exposed work, each outlet box, junction box, or fitting shall be securely fastened in place.(D) Openings. Each outlet box, junction box, or fitting having a volume of over 18 cu in. (295.7 cm3) shall be provided with at least one knockout opening on each face, side, and back for the purpose of facilitating the removal of knockout closures.(E) Nonmetallic Boxes. Nonmetallic outlet boxes, junction boxes, or fittings shall be listed as suitable for the location and application.

Interpretation

314.2 is referring to both round and octagonal electrical boxes.

Octagonal boxes

These boxes are typically used for ceiling lighting fixtures and switches. They have knockouts on the sides to allow for the entry of conduit or cables from any direction.

Round boxes: These boxes are typically used for wall outlets and switches. They have a single knockout on the bottom for the entry of conduit or cables.The reason why octagonal boxes have knockouts on the sides is to provide flexibility in the installation of conduit or cables. For example, if a conduit is coming into the box from the side, the installer can simply remove a knockout and insert the conduit into the box.It is important to note that not all octagonal boxes have knockouts on all sides. Some boxes may only have knockouts on one or two sides. When choosing an octagonal box, it is important to select a box that has the appropriate number and location of knockouts for the specific installation. Flag for review