Set Square
A set square is a ruler used to accurately check and draw right-angled lines, parallel lines, and measurements in pattern making and fabric marking, based on two sides that intersect at right angles.
Contents6 sections
Definition and Overview
A set square is a ruler with two sides joined at a right angle. It is used for drafting, marking before cutting, and checking seam allowances, because it lets you draw lines while confirming right angles against pattern paper or the edge of fabric. It is commonly marked with graduations on both the long and short sides.
It is also called a right-angle ruler. A tailor's square may refer to a larger set square used in dressmaking and pattern making, but in sales settings the two are sometimes treated as synonymous.
How to Use
When making patterns, align one side exactly with the edge of the paper or a reference line, and draw along the other side. When drawing a parallel line at a fixed distance from a reference line, take measurements at multiple points and connect the marks with the set square.
When marking fabric, taking a right angle based on the grain line or selvage makes it easier to check for distortion in the cutting line. However, the fabric edge itself is not always a precise straight line, so check the grain line as needed as well.
- On pattern paper, draw lines along the side with a pencil or mechanical pencil.
- On fabric, choose a marking tool suitable for fabric, such as tailor's chalk or a washable chalk pen.
- Before drawing a line, hold the ruler firmly so it does not shift.
Types and How to Choose
Materials include transparent resin and metal. Transparent ones make it easier to align while looking at the lines or grid underneath, while metal ones tend to resist damage. For the intended application, check the necessary length of the long and short sides and how easy the graduations are to read.
For garment blocks or large patterns, a type with extra length on the long side is convenient. For small items or a narrow worktable, a compact type that is easy to handle is suitable. If the sides are too thick, the drawing position may shift, so check the cross-sectional shape as well.
- Graduation marks start close to the end of the side and are easy to read
- Transparent enough to make it easy to see reference lines and the grid
- Non-slip and easy to keep in position during work
- Dimensions that suit the pattern or cutting table being used
Care and Safety Notes
After use, wipe off any chalk or paper dust with a soft cloth. Resin rulers may warp or deform under high heat or direct sunlight, so store them on a flat surface and do not leave them near a heat source.
If dropped or subjected to a strong impact, the corners may chip or the right-angle accuracy may be affected. When using the edge of the ruler as a cutter guide, be careful not to let the blade slip, and check whether the ruler is suitable for cutter work.
Differences from Similar Terms
A grid ruler is a straight ruler that uses the grid on its surface to check parallel lines, angles, and measurements. A set square is characterized by using the right angle formed by its two sides, making it suitable for quickly creating right-angle lines.
A curve ruler is used for drawing curves such as necklines, armholes, and crotch curves, and its role differs from that of a set square, which handles straight lines and right angles. A tape measure is a tool for flexibly measuring body or fabric length, and it is used separately from a set square when establishing a line reference.
Frequently Asked Questions
How do you take a right angle to the grain line of fabric with a set square?
First, align one side of the ruler with a reliable reference line such as the selvage or an existing grain line. Check the right-angle direction with the other side, and mark the needed position. Since the selvage can be distorted, check the grain line at multiple points before deciding the cutting line.
Which should I choose, a set square or a grid ruler?
If you often make pattern corners or vertical lines based on right angles, a set square is suitable. If you repeatedly draw parallel lines or want to check detailed measurements against a grid, a grid ruler is convenient. Using both according to the application makes the work easier.
