A T-square is a good tool to have for home improvement projects where right angles are needed such as tile work.
The definition of a right angle is the meeting point between two perpendicular straight lines.
An example of a right angle is a 90º angle.
an angle of 90 degrees; angle made by the meeting of two straight lines perpendicular to each other
An angle formed by the perpendicular intersection of two straight lines; an angle of 90°.