Boxes may or may not be provided with clamps. When clamps are provided,
the carton is marked to indicate the type of wiring system or combination
of systems for which they have been tested. The clamps are marked
with the following letters or combinations thereof to indicate that they are
suitable for use with nonmetallic sheathed cable ??N?? or flexible tubing
(loom) ??T.?? Clamps suitable for nonmetallic sheathed cable are also suitable
for multiconductor underground feeder and branch circuit cable where used
in dry locations unless the box or smallest unit carton is marked ??Nonmetallic
Sheathed Cable Only.?? Clamps have been tested for securing only one
cable per clamp, except multiple section clamps are considered suitable for
securing one cable under each section of the clamp, each cable entering a
separate knockout.