What type of tool has two arms called the Blade and the Tongue, and is used to check the accuracy of an angle?

The tool designed specifically to check the accuracy of an angle and characterized by its two arms, referred to as the Blade and the Tongue, is the square. A square is commonly used in woodworking and construction to ensure that angles are exactly 90 degrees, which is vital for creating well-structured projects. The Blade of the square is the longer arm that typically serves as a reference edge, while the Tongue is shorter and extends perpendicular to the Blade, allowing users to mark and measure right angles accurately.

Other tools listed have different purposes: a sliding T-bevel is adjustable, allowing for the measurement of angles other than 90 degrees; a level is used to check the horizontal or vertical alignment of surfaces; and a plumb bob is utilized for establishing a vertical reference line. Thus, the square is the only tool among them specifically aimed at ensuring angle accuracy.