loodlijn

Loodlijn is a Dutch term that can refer to two related measuring tools, both depending on a weight and the force of gravity to establish a reference line. The most common meaning is plumb line, a line with a weight (often called a plumb bob) at its end. When suspended from a fixed point, the weight pulls the line taut and the line aligns with the vertical. This vertical reference is used to check whether surfaces or structures are truly vertical, to transfer elevations from a known point to another, and to align elements such as walls, columns, or door frames. While modern construction frequently relies on spirit levels and laser devices, the plumb line remains a simple, reliable tool in settings without power or where a direct vertical reference is needed.

The second sense, more historical and nautical, refers to a depth-sounding line. This is a line marked at regular intervals and weighted at the end, lowered from a boat until the weight touches the seabed. The depth is read from the markings on the line. Such lead lines were essential for early hydrography and navigation, helping mariners determine water depth and assist in charting coastal waters. With advances in sonar and electronic depth finders, the use of a traditional sounding line has diminished, but it remains part of maritime history and basic seamanship training.

Etymology derives from lood (lead) and lijn (line). In practice, loodlijn commonly denotes the plumb line, while historical or nautical contexts may emphasize the sounding line aspect.