The different methods of wiring which are now approved by the National Board of Fire Underwriters, may be classified under four general heads, as follows:

1. Wires Run Concealed in Conduits.

2. Wires Run in Moulding.

3. Concealed Knob and Tube Wiring.

4. Wires Run Exposed on Insulators.

Wires Run Concealed In Conduits

Under this general head, will be included the following:

(a) Wires run in rigid conduits.

(b) Wires run in flexible metal conduits.

(c) Armored cable.