What tool is best for drawing a 90 degree angle?

The T-Square is the most effective tool for drawing a 90-degree angle because it has a straight edge that is aligned with the vertical or horizontal lines on a drafting table. When using a T-Square, you can easily draw perpendicular lines by connecting the edge of the square with the straight edge to create a perfect right angle. This tool is specifically designed for creating accurate lines and angles in architectural and technical drawing, making it ideal for tasks that require precision.

In contrast, a compass is primarily used for drawing arcs and circles, not for constructing angles. A ruler is useful for drawing straight lines and measuring lengths, but it does not inherently assist in forming specific angles like the T-Square does. A protractor is designed to measure angles but does not provide a direct method for drawing a 90-degree angle without additional reference lines. Thus, for the specific task of drawing a 90-degree angle, the T-Square stands out as the best choice.