Measuring and Layout Tools

Linear Measuring Rules, Tapes, and Squares

Accurate layout begins with standard linear measuring tools. In shop environments, technicians rely on steel rules rather than flexible household rulers. A standard steel rule is marked with fractions of an inch, commonly divided down to sixteenths, thirty-seconds, or sixty-fourths of an inch. When working with metric specifications, a metric steel rule is graduated in millimeters and centimeters. For extended distances, a tape measure is the standard choice. If you examine the end of a tape measure, you will notice that the metal hook is loosely riveted. This hook is intentionally loose so it can shift by its own thickness, ensuring accurate inside measurements (when pushing the hook against a surface) and outside measurements (when hooking over an edge).

Certain tasks require a rigid measuring tool rather than a flexible tape. A folding rule, also known as a zigzag rule, is a rigid measuring stick made of hinged wooden or fiberglass sections. Because it holds its shape without buckling, a folding rule is especially useful for measuring overhead or vertical spans. Shop Information does not contribute to the AFQT score, which uses AR, MK, WK, and PC; knowing these tools can help with Shop Information questions, while each military branch sets its own job qualifications and may change them.

Squaring tools allow you to check edges and mark angles accurately. A try square features a fixed 90-degree angle between its blade and handle and is used primarily in woodworking to check edges and mark perpendicular lines. For larger tasks, a framing square, also known as a carpenter's square, provides an L-shaped steel or aluminum body used for laying out rafters, stairs, and sheet goods. The longer arm of a framing square is called the body, and the shorter arm is called the tongue. For trim work, a miter square provides a fixed 45-degree angle blade used specifically for laying out miter cuts for picture frames, molding, and trim.

Other squares offer versatile functions. A combination square features a grooved steel blade and a sliding head that measures both 90-degree and 45-degree angles. Its head often includes a bubble level and a removable scriber for marking lines directly onto a workpiece. A speed square, or rafter square, is a triangular layout tool used for quickly marking 45-degree and 90-degree angles and serving as a saw guide. When an angle is not fixed at 45 or 90 degrees, a sliding T-bevel is used. A sliding T-bevel has a blade that locks at an adjustable angle so you can copy or transfer an angle; you need a protractor to find the angle in degrees.