Square means at a right angle, that is exactly 90 degrees. A joint, corner, or wall is square when the two parts stand perpendicular to each other.
Characteristics
Squareness is about the angle between two lines, surfaces, or parts: if they meet at exactly 90 degrees, the join is square. You can check it with a try square, or for larger dimensions with the 3-4-5 method. From the corner, measure 3 units along one line and 4 along the other; if the diagonal between them is exactly 5 units, the angle is perfectly square. This follows from the Pythagorean theorem (3² + 4² = 5²) and works with any consistent unit, such as metres.
Applications
Setting out square is essential for foundations, walls, window and door frames, and tiling. When setting out a building, you check that the load-bearing walls are square before building further, because an out-of-square start carries through the whole structure. When laying tiles or fitting a frame, working square gives clean, tight joins. For small parts a try square is enough; for large dimensions the 3-4-5 method is more reliable.
Related terms
- try square
- spirit level
- plumb line
- setting out
- right angle
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