Pattresses

It can be happen that an outlets , such as a socket outlets or ceiling rose , has to be placed a small distance in front of the structure available to support it . This can happen , for example , when a wiring system is installed on the surface of walls and ceilings and there is a step in the surface which the wiringt cannot follow , so that it has to be supported off the surface . It is then necessary for some sort of distance piece to take up the gap between the fitting and the surface behind it . Standard components are available for this and are known as pattresses . A box for use with a circular socket outlet is shown in Figure 1,17 , which also gives a sketch showing the use of the box with surface conduit . The inclusion of the box makes it possible for the cables to enter the socket outlet from the back , whereas without it , there would be an untidy junction of the conduit with the bottom of the socket outlet  . It is now fairly standard practice in commercial situations to install trunking which incorporates the socket outlets .