What instrument would you use to measure a 90° bend on a sheet-metal bracket?

To measure a 90° bend on a sheet-metal bracket accurately, a try square is the most suitable instrument. A try square is specifically designed to check the squareness and angles of materials. It consists of a right-angled triangle-shaped blade fixed to a handle, allowing it to rest against one edge of the material while the other leg extends out to determine if the angle is indeed 90°. Its design ensures precision in aligning and verifying right angles, making it ideal for confirming that a bend is perfectly perpendicular, which is crucial in sheet-metalwork for ensuring proper fit and structural integrity.

While other tools like protractors and angle finders can measure angles, they are typically more suited for measuring angles other than 90° or providing a range of angle measurements rather than strictly confirming the right angle. Calipers, on the other hand, are primarily used for measuring distances and thicknesses rather than checking angles. Thus, the try square stands out as the most effective tool for ensuring the accuracy of a 90° bend in metalwork.