Definitions of reference geometries
Many cases are possible. For more information, it is advisable to refer to the FreeCAD reference documentation on reference points, reference lines, reference planes and coordinate system.
Example of use 1
We want to create a sketch
in a plane passing through A and B
perpendicular to the sketch plane ABC.
For this, we have added in this master
sketch a BD segment perpendicular
to AB (original B).
The sketch being closed, select
the BD segment then click on .
A new reference plane appears.
You must then select this plane then
click on to create the sketch
See another example.