Trenching is a form of excavation in which a large hole is dug; the hole itself is usually quite deep but not very wide, and it is often dug to be long. Trenching is common in construction, especially when installing underground pipes, wires, or structural supports. The practice of trenching is also common in military applications to protect front line troops from gunfire or other hazards. Large trenches can be damaging to a landscape if not properly dug and re-filled after use, and digging trenches is a hazardous job, as the walls of the trench are prone to cave-ins if not properly supported on either side.
A trench digger can be used for trenching, or it may be done by hand with a shovel or pickaxe. Larger trenches are difficult to dig by hand, so a motorized machine has been specially designed to do the job. Trench diggers come in a wide range of sizes to accommodate the digging of many different sizes of trench. Smaller trench diggers are small enough to be operated by one person pushing the digger along the area to be trenched. Larger trench diggers, common in construction settings, are massive machines that must be driven. A large, saw-like arm is lowered to the ground to dig the trench.
A trenching differs from simple hole digging because a trench is generally not as wide as it is deep. It is also usually very long, rather than isolated in one area or built in a circular shape. A trench's shape is exactly what makes it hazardous: the walls of the trench are long and unsupported, and since the hole is deep, the lack of support runs deep as well. Trenches cave in easily, causing a hazardous work environment for anyone inside the trench. In construction sites, metal supports are usually placed inside the trench to keep it from caving in.
In warfare, trenching was often done to provide an obstruction between opposing forces. With the advent of firearms, the trenches were used as shelter from bullets and shrapnel. In many cases, elaborate mazes of trenches were built, often by hand using shovels and other hand tools, to provide more strategic positioning against the enemy. Many times throughout history, trenches were combined with underground tunnels to allow troops to move from one site to another without being detected. The practice of trenching has been around for thousands of years for military, farming, and construction purposes.