nog

A nog is a short section of squared timber, typically 4 to 6 inches on each face, used as a vertical or near-vertical prop to support the roof of an underground mine. Unlike round pit props or the flexible timber used in temporary shoring, a nog is shaped with a broadaxe or saw into a square or rectangular cross-section, making it easier to stack, drive, and wedge in place against uneven stone surfaces. The squared profile also allows the timber to be checked and measured for soundness before installation, a practical advantage in environments where failure of a single prop can cascade into collapse.

In coal and metal mines, nogs were arranged in clusters called cribbing or in lines called props. A single workings face might require hundreds of nogs to be installed, driven home with iron wedges beneath the cap (the horizontal timber resting on the props), and then released from below as the face advanced and was abandoned. The timber was usually pine, spruce, or other softwood that could be squared efficiently and handled by a single miner. Nogs were cheaper than dressed building lumber because the finish did not need to be precise, only square enough to wedge properly.

Pit Props and Modern Displacement

By the late 19th and 20th centuries, the term nog became less common as pit props, round or minimally squared timbers, and later steel arch supports and resin-bonded bolts replaced traditional timber cribbing in most mechanized mines. However, in small underground quarries, slate mines, and historical documentation of older collieries, references to nogs persist. The distinction between a nog and a simple pit prop was never absolute; regional dialect and mine management practice determined which term was preferred, and a squared prop might be called either depending on the operator's background.

The word itself likely derives from an Old English term for a block or peg, related to the wooden pegs used in other trades. In carpentry outside the mine, a nog can also refer to a wooden block used to anchor bolts or fill cavities in masonry and timber framing, though this usage is even more archaic and largely replaced by metal inserts and chemical anchors.