A margin trowel is a small, flat tool used primarily in masonry and plastering. It features a narrow blade, typically around 4 to 6 inches wide, which allows for precise application and smoothing of materials like mortar and plaster. The handle is usually made of wood or plastic, providing a comfortable grip for detailed work in tight spaces. This tool is essential for finishing edges and corners where larger trowels may not fit. It is also useful for mixing small amounts of mortar or cement and for cleaning up excess material. Overall, the margin trowel is a versatile instrument for professionals and DIY enthusiasts alike.