Trunking is a rectangular enclosure with a removable lid, so cables can be laid in and added later. Conduit is a round tube that cables are drawn through, giving more enclosed protection. Trunking suits larger numbers of cables and easy access, while conduit is often used for neat, robust runs to individual points.

Cable tray is used to support large numbers of cables, or heavy cables such as SWA, in plant rooms, ceiling voids and industrial buildings. It is open, so cables stay cool and easy to add or inspect. Trunking encloses cables and is better where they need to be hidden or protected.

Outdoor runs commonly use galvanised steel conduit, PVC-coated flexible conduit, UV-stable PVC conduit or armoured cable clipped direct. Choose products the manufacturer rates for external use, and use IP-rated boxes and glands at terminations to keep water out. Check current wiring regulations for the environment involved.

Low smoke and fume (LSF) or low smoke zero halogen products are often specified for public buildings, escape routes, hospitals, schools and enclosed spaces, because they release less smoke and fewer harmful gases in a fire. Your project specification or the building's fire strategy will say whether they are required.

SWA terminations usually need a correctly sized armoured cable gland, a shroud, an earth tag to bond the armour, and sometimes lugs for larger conductors. Where a cable is joined underground, a purpose-made resin joint kit is used. Follow the gland and cable manufacturers' instructions.

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Trunking is sized so the cables fill no more than a set proportion of its internal space, which allows for heat dissipation and future additions. A commonly used guide is around 45% fill, but the exact limit depends on the cable types and installation. Use the manufacturer's capacity tables and current wiring regulations, and allow spare room if more circuits may be added later.

The number refers to the outside diameter. 20mm conduit is common for lighting and small power circuits, while 25mm holds more or larger cables, such as for submains or grouped circuits. The right size depends on the number and size of cables, the length of the run and the number of bends. Check capacity tables before choosing.

Current wiring regulations require cables in escape routes and many other areas to be supported so they will not fall and obstruct people or firefighters during a fire. In practice, this means using metal or fire-resistant clips, ties and supports rather than plastic alone. Check current wiring regulations for where this applies and which fixings are acceptable.

SWA cable is usually terminated with a BW gland indoors or a CW gland outdoors and in damp locations, sized to the cable's overall diameter and armour. Add a shroud to protect the gland, and earth tags or banjos to bond the armour where required. Matching locknuts and washers complete the termination. Check the gland size chart before ordering.