Pattress

Pattresses contain devices for input (switches) and output (sockets and fixtures), with transfer managed by junction boxes.

In the United Kingdom, surface-mounted boxes in particular are often made from urea-formaldehyde resin or alternatively PVC and usually white.

Although cables may be joined inside pattress boxes, due simply to their presence at convenient points in the wiring, their main purpose is to accommodate switches and sockets.

In North America, outlet boxes are rectangular in shape and are available in different sizes, to accommodate varying numbers of switches.

They are typically designed with nail or screw holes to attach directly to wall studs.

In most of Europe, outlet boxes are round, with a standard diameter of 68 mm, to accommodate a single insert.

This is an advantage especially when installing outlet boxes in brick or concrete walls, which are much more common in Europe than in North America.

Boxes intended for drywall always have parsellas, similar to the North American old work type (the distinction between old and new work is not used in Europe), as the round shape of the boxes and prevalence of light-gauge steel framing in modern drywall make nailing to a stud impractical.

Single gang boxes for installation in plasterboard are of the standard European type.

Boxes for installation in brick walls are rectangular in shape and can be connected to form a chain, similar to their standard European counterparts.

Two-module boxes are similar in size to those used in Europe and the British Isles, and can be used interchangeably.

Single-module boxes are available for installation in metal profiles of modular office walls.