Editing Pillar box (section)

==Construction==
[[File:PB Cap.jpg|thumb|left|Cast iron cap of a PB42/1 sits atop the box and is secured by bolts]]
[[File:E8R Door.jpg|thumb|upright|This rare [[Edward VIII]] pillar box door shows the built-in posting aperture, collection plate and the royal cypher at Colne Valley Postal History Museum, [[Halstead]], [[Essex]]]]

Most traditional British pillar boxes produced after 1905 are made of [[cast iron]] and are cylindrical. Other shapes have been used: the hexagonal Penfolds, rectangular boxes that have not proved to be popular, and an oval shape that is used mainly for the large "double aperture" boxes most often seen in large cities like London<ref name=bath>{{cite web |url= http://www.bathpostalmuseum.co.uk/history-of-the-post-box.html |publisher=Bath Postal Museum |title=History of the British Postbox |access-date=19 November 2009}}</ref> and [[Dublin]].<ref>{{cite web |url= http://www.lbsg.org/shapes-r.shtml |title=Shapes |publisher=Letter Box Study Group |access-date=22 March 2007}}</ref> In recent years boxes manufactured in [[glass-fibre]] or [[acrylonitrile butadiene styrene]] (ABS) plastic have been produced that do not follow these general outlines. These are for use in secure indoor locations such as [[supermarket]]s.<ref>{{cite web |url= http://www.lbsg.org/materials-r.shtml |title=Materials |publisher=Letter Box Study Group |access-date=22 March 2007}}</ref>

Cast iron pillar box construction comprises three distinct main parts:

The cap sits on top of the carcass and is usually bolted down from inside. Some designs after 1965 do not have a separate cap. Caps can also be fitted with a separate bracket, normally of cast iron, which supports a Post Office Direction sign (POD) indicating the nearest Post Office.

The door contains the aperture or posting slot. It is hinged, should display the [[royal cypher]] of the monarch who was reigning at the time of installation, and may also be fitted with a [[collection plate (postal)|collection plate]] showing the times of collection from that location. It is fitted with a brass security lock on the inside. The contractor for these locks has been the [[Chubb Locks]] company for many years. They are five-lever locks and each one can exhibit more than 6,500 combinations. There is no [[skeleton key]] for these locks. Each post box has its own set of keys and postal workers have to carry large bunches with them when clearing the boxes.

The carcass or body of the box supports the door and cap, and may protrude substantially down below ground level. This provides security and stability to the pillar box. There is a wirework cage inside to prevent mail falling out when the door is opened, a hinged letter chute to allow mail to fall into the collecting bag or sack, and a serrated hand-guard to prevent unauthorised tampering with the mail through the aperture.