A ruler level, also known as a combination square or a multi - function ruler, is a versatile hand - held tool that combines the functions of a ruler for measuring lengths and a spirit level for determining the horizontal or vertical alignment. It typically consists of a straight, graduated blade and a small vial filled with a liquid (usually alcohol or oil) containing an air bubble. This tool is widely used in construction, woodworking, plumbing, and other trades where accurate measurements and level - checking are essential.
The concept of using a straight edge for measuring and a device to determine levelness has ancient origins. Early Egyptians and Romans used simple straight rods for measuring lengths. The spirit level, in its basic form, was likely developed in the 17th century. The combination of a ruler and a level into one tool, the ruler level, became more prevalent as craftsmanship and construction techniques advanced. As materials and manufacturing processes improved over time, ruler levels became more accurate, durable, and ergonomic, with better - defined graduations and more precise level vials.
Length Measurement: The ruler portion of the tool has calibrated markings, usually in inches or centimeters. These markings are based on standard measurement systems. When measuring an object, one end of the ruler is placed at the starting point of the object, and the length is determined by reading the value at the other end of the object against the markings on the ruler.
Level and Plumb Detection: The spirit level vial works on the principle of gravity. The vial is slightly curved, and the air bubble inside it will always rise to the highest point. When the tool is placed on a surface, if the bubble is centered between two marked lines on the vial, the surface is level (in the case of a horizontal - checking vial) or plumb (in the case of a vertical - checking vial). This is because the force of gravity causes the bubble to align itself with the vertical axis of the earth.