Architectural and construction drawings are drawn to scale, meaning a measurement on paper, such as 1 centimeter, represents a larger real-world distance, such as 1 meter, with the scale ratio always noted on the drawing; misreading scale is one of the most common sources of costly on-site errors. Plans use standard symbols for doors, windows, walls, and fixtures, and typically include separate views such as the floor plan (a top-down view), elevations (side views), and sections (a vertical slice through the building). On-site measurement relies on a few essential tools: a tape measure for lengths, a spirit level to check that a surface is perfectly horizontal or vertical, and a builder's square to check that corners form a true right angle. In Nigeria and most of Africa, the metric system (meters, centimeters, millimeters) is the standard for construction measurement, though some imported plans or materials may still reference imperial units like feet and inches, making basic unit conversion a practical skill.