hello!! Yesterday I got Seamly2D, I´ve never used it, I usually made my patterns with Illustrator but it is very complicated at the moment of transformations.
I dont speak English, just a little so almost tutorial on Youtube are in English…so sorry my frustation 
I would like to know how can I mesure this ? I need to create a point on this intersection but I dont kow how to make it. thank you very much.
Hello, I am also new using the software, I will leave you images of the way I would do it, if you want to transfer the measurement of the line c7-b to the line ct-Tf you can use the option of perpendicular point along a line , it would look like in the second image that I leave you, if you want to make a point of intersection between the line c7-Tf and line B you can use the option point of intersection of line and axis (third image), I hope I have helped you, sure there is another way to do it, but they are the ones I know so far I don’t speak English either, my language is Spanish. regards
to see the complete images click on each one of them!
hola!! ahora mismo estaba viendo tu video de la camisita de niño, voy despacio pq mientras avanza tu video lo aplico a mi base de vestido. leere tu consejo gracias!
graciasssss
Here is another way to do this:
This tool will place a point at any intersection of 2 lines even if there are no lines drawn:
A small tip… If you are uncertain what to do next when using a tool, look in the bottom left corner, there is normally a small instruction to help you to use the tool that you have chosen:
thank you very much!! I gonna use it too!
