How to use the humble L-square or tailor’s ruler

Nearly everyone has an L-Square made by Fairgate, sometimes called a tailor’s square or rule for pattern drafting; these are indispensable. Today I’d planned to tell you all about the various uses of them but time has a way of catching up with me. Instead, I’ll tell you about them in the context in which the subject came up. Below is a drawing of one. The typical square is 14″ X 24″ making them difficult to photograph. A larger view is here.

The question was:

I was wondering what is the best way to make half scale patterns. Should I only draft half of every measurement when doing a basic block? If I have a measurement of 14″ the ruler will break it down to 7″?

The answer is yes. The ruler has a built in math cheat sheet. Below are some of the scales marked off. The ruler also breaks down into 6ths and 12ths on the long arm and 8ths and 16ths on the short arm. See below if not from here.

To easily draw only half of 14, you draw from the zero point, up to the 14 on the halves portion of the scale. This will equal 7″ as shown below.

See, it’s very simple to cheat on figuring measures with your L-square.

Now maybe when I have more time, I can explain how this tool is used with archaic pattern books to draft patterns. For example, if you’ve ever read the texts of these older books (meaning before 1960), you’ll see frequent directions to draw a line that is 1/6th of breast or something similar. This would mean to draw a length from zero up the number on the scale of 6ths that represents your chest. Nifty, huh?

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10 Comments on "How to use the humble L-square or tailor’s ruler"

antonella vassallo
10 months 12 days ago

hi there, can anyone remind me how to find the scale measurement of the bodies? tks in advance

1 year 7 months ago

I’d mentioned as much in another post, don’t know which now but probably one related to draping on half scale forms.

There is a trade off. Only certain weights will behave reasonably well in half scale. Georgette is one that comes to mind.

1 year 7 months ago

When drafting to half size, and making a garment for the dummy, do you not lose the drape of the fabric?

2 years 1 month ago

Can someone please tell me if the same principle applies if you want to measure a 1/3rd or a 16th, 4th and so on? Thank you in advance.