Hi, how can i create the correct mirroring of the seam allowance.
The Seam allowance of 2,5 cm needs to be angled outwards (blue sketched line). I tried all possible angle settings in the properties in the pattern pieces
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Welcome to Seamly!
This difficulty was actually mentioned a couple days ago in this post:: Draw paralelle in draft modus - #3 by Douglas
In short, if you want your seam allowance to flare, you have to draft the flare in.
Although it’s often handy to abuse the seam-allowance feature to avoid drafting a hem, a hem is not actually a seam-allowance, & should be drafted in, much like the sleeve itself. The Mirror Objects by Line tool is often handy in this spot.
I hope that, (particularly the linked post,) is helpful. Please ask for clarification as needed. Happy drafting!
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Okay thanks, i was afraid that it wouldn’t be that easy to install a mirrored hem allowance.
But even with regular seam allowances, the calculation at corners and curves is often incorrect. Are therefore some Bugfix releases planed in further versions?
And i also missing a simple Measuring function for curves and any Point i want. Like a kind of digital ruler to do plausibility checks.
But at the First look seamly2d seams to be a good Software! Thanks for your Work! I look forward to the further development of the software.
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But either way you’re adding points to demarcate it in Draft mode, yes?
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Yes. With a custom seam allowance you would make your points say above a cuff line, where then when you add a seam allowance of say 2"… the whole seam allowance is cross hatched VS adding the cuff below the hem line.
So you get this:
and not this:
Note… I fudged the top pic as I didn’t want to find the pattern and figure out ther custom SA. 
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Hi me again,
all mention the custom seam allowance. I tried to work with this. It sounds quite promising but how the h. . . is it working.
I can not find an proper explanation (Online, Youtube, manuals etc.) how is this working???
Piece is A5, A10, Spl_A10_ . . . .
Internal path, custom seam allowance A5, A10, Spl_ . . . , A20a, A20 / saved as Back hem facing
Pattern piece :
it shows the automatic seam allowance. Tried also other options, not the wished or descripted results. How this works?
P.S.: @Grace, @Douglas @pnvie
Maybe it would save a lot of work/answers if you put some effort into a FAQ page/manual. There are a lot of questions that are just basic. I appreciate your enthusiasm. I recommend you invest your valuable time in approving Seamly2D instead of being friendly.
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Hi again, @MG2024. That’s not nice. We like to be friendly, and, like you, we all have day jobs and offer our assistance purely because we love the software and want people to get the most out of it, not because there’s some magic money tree somewhere that’s paying us to be here so that we can give up our day jobs.
With that said, let’s move on…
This forum is the FAQ. At the top right, there’s a magnifying glass. This is the search. Click on it and you can search through many topics on just about everything in the software and patternmaking.
Then there’s the User manual in the Wiki (link at the top of the page) where there are videos listed, on Youtube, in a number of languages that our amazing users have created and published.
Recently, @JCDesign has been updating the Wiki Seamly2D and SeamlyME user manuals.
Currently, the PDF user manuals are really old. I wrote them in 2017 with a lot of help from searching the forum and trial & tribulation while I was learning Seamly2D, however the information is still quite helpful and I’ll get onto writing new manuals later this year, once things have calmed down at my day-job (normally around October, November, December since I work for a number of small companies, auditing their books and doing the income tax, etc.).
So let’s all be friendly and make this a happy haven for everyone who is passionate about patternmaking - be it their career or their hobby.
And now onto the subject at hand…
Ok, so you want to add a hem allowance of (say) 2cm below the hemline, that needs to be folded over and hemmed in the construction of the garment. The one side is slanted and the other side is a curve.
Firstly you need to place a guide point to establish the 2cm level where the stitches will go:
In the case of trousers, I’d use the Crease Line to do this and the Point - On Line Tool:
On the slanted edge, I’d use the Intersect - Line and Axis tool. Click the tool, select the 1st point of the line and then the 2nd point of the line, then select the point of your axis (the new point at 2cm from the hemline). Adjust the angle, if necessary:
The next step is to use the Intersect - Curve and Axis tool. Click the tool, select the curve and then the axis point and, once again, adjust the angle to suit the other side:
What you now have is the line where the hem will be stitched:
Now you are ready to mirror that section to the area below the Hem Line. Pick up the Mirror Objects by Axis tool. Select the curve, A8 & A7 (items to be mirrored), hit Enter, then A3 (or A4 or A2, it doesn’t matter), hit Enter and Select (in this case) Horizontal (if this isn’t a Vertical/Horizontal case, then use the Mirror Objects by Line tool):
Now you can use the Line Between 2 Points tool to connect the dots:
Now, if you create your pattern piece, you can add internal paths for the Hem Stitch Line and the Hem Line. Normally, you’ll still need to add a seam allowance for the bit that gets folded under:
And there you have it. And here is the file that I created to show you:
Hem Added.sm2d (8.0 KB)
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Hi Grace, Sorry u got my point wrong. I am aware that u all doing this for good. I just wanted to save u time.
Unfortunately in all Faq, pdf, YouTube as on the wiki i was not capable to find a description of using the piece option custom seam allowance as Douglas mentioned.
Right now i add a integrated hem facing on ur well explained methode. As far I get there is an option to define the facing as an custom seam allowance which can be added in piece mode to the pattern piece.
Gr Michael
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Hi, @MG2024. I’m sorry if I got your point wrong, but I thought it best to explain things nicely 
To add FAQ’s to the Wiki, everyone has a different problem according to their methods of pattern making and everyone describes their problem in different ways. That’s why I try to explain to each person how to solve their problem, even if I need to repeat myself over and over throughout the forum - at least each question gets replied to in the latest version of the software.
I normally define my facings on the pattern piece in draft mode, create the facings pattern pieces and then make the default seam allowance (inside the pattern piece) 3mm less than what I used on the pattern piece, to pull the stitch line to the inside of the garment.
Since you’ve used my method to create the hem, the added seam allowance will follow the outer lines. To have the piece that you fold under fit into the edges, I’d suggest that you repeat the mirror exercise for the depth of the seam allowance and then remove any seam allowance at the cut line for the hem.
P.S. I use this same method to create the button stand on upper garments.