for 3" octagon boxes are:
3-0 flat blank covers
3-0 duplex receptacle covers
3-0 flat with 1/2" knockout covers
3-0 single receptacle covers
The covers for 4" octagon boxes are:
4-0 flat blank covers
4-0 duplex receptacle covers
4-0 flat with 1/2"
4-0 flat with 3/4" knockout covers
4-0 single receptacle covers
4-0 twist-lock receptacle covers
4-0 raised sign receptacle covers
4-0 1/4" raised plaster ring
4-0 1/2" raised plaster
5/8" raised plaster ring
4-0 3/4" raised plaster ring
4-0 1" raised plaster ring
4-0 1-1/4" raised plaster ring
4-0 1/2" raised blank cover
4-0 1/2" raised one device
Covers for 4-S outlet boxes
are similar to 4-0 covers except that they're square and many more types are available.
Square covers for 4-11/16" boxes also come in types that will meet almost any
Special Outlet Boxes
Special outlet boxes are
available to cover applications not mentioned so far in this section. Ganged boxes are used when more than one wiring device
is to be installed.
Multi-ganged boxes can be one-piece or welded plated steel. They have 1/2" and 3/4" knockouts and the mounting
holes are punched. Most have two 8-32 machine screws at one end and two holding tabs at the other end to hold the switch ring.
The switch ring is usually raised 3/4".
The multi-ganged box ranges from two-gang to ten-gang. They're generally used for multiple
switches. But occasionally you'll see them used for multiple receptacles.
Another special outlet box is the masonry box. It's made of plated steel, is stamped
with knockouts and has mounting holes punched. The boxes are usually single- or two-gang and are deep enough so that they
can be flush mounted and still intercept conduit that's run through the cavity of a masonry unit. The top and bottom edge
of the box are turned inward and are tapped for 6-32 machine screws that hold the wiring device in place.
There are through boxes
for masonry work that permit mounting devices back-to-back on both sides of a wall. They measure 3-1/2" high and 7-1/2"
deep. Both the front and back of the box are made to receive wiring devices.