A try square is a simple but essential workshop tool used to check and mark 90° right angles. It has a long, thin metal blade fixed at a right angle to a thicker stock, often made of wood, metal, or plastic. Accurate right angles matter because small layout errors can make joints weak, surfaces uneven, and assembled parts misaligned.
In woodworking, metalworking, and general fabrication, the try square helps turn careful measurement into accurate work.
Key Facts
- A try square checks and marks 90° angles between two surfaces or lines.
- The blade is the long, thin metal ruler used for marking and checking straight edges.
- The stock is the thicker handle that rests against the edge of the workpiece.
- For a right triangle check, a^2 + b^2 = c^2 confirms a 90° angle.
- Percent error = |measured value - true value| / true value × 100.
- A larger contact area between stock and workpiece helps improve squareness and stability.
Vocabulary
- Try square
- A measuring and marking tool used to check and draw accurate 90° angles.
- Blade
- The long, flat metal part of a try square used as a straightedge and marking guide.
- Stock
- The thicker part of a try square that rests against the edge of the workpiece.
- Right angle
- An angle that measures exactly 90 degrees.
- Squareness
- The condition of two edges, faces, or lines meeting at a true 90° angle.
Common Mistakes to Avoid
- Holding the stock away from the edge, because the try square cannot show a true 90° reference unless the stock is seated firmly against a straight edge.
- Using a damaged or bent blade, because even a small bend can make marked lines inaccurate across the length of the workpiece.
- Marking from a rough or unprepared edge, because the square transfers the error from that edge into every line you draw.
- Assuming every try square is accurate forever, because drops, wear, and poor storage can shift the blade out of square and require checking.
Practice Questions
- 1 A board is marked with a try square line across a width of 180 mm. If the line is 2 mm out of position at the far edge, what is the approximate error per 100 mm of width?
- 2 To check a corner using the 3-4-5 method, one side is marked 300 mm and the other is marked 400 mm. What diagonal distance should confirm a right angle?
- 3 A student presses the blade against the workpiece but leaves the stock slightly lifted from the edge. Explain how this affects the accuracy of the marked line and how to correct the technique.