This page explains the Sketch and it's tools.
Sketches are 2D vector drawings which are used as templates for modifiers. They can be extruded or revolved to create solid shapes. They can also be applied to surfaces of existing bodies in order to be used as templates for e.g. punching or embossing.
Sketches consist of a series of curve segments that are clearly defined and delimited by points. Segments themselves are therefore parameterless. For example, a circle is not defined by the center and the radius, but by the center and a rim point. However, parameters can be mapped using constraints, which in this case attempt to achieve a certain radius. Later more.
Sketches can also have construction lines. These can be included in the sketch editor as normal segments, but are hidden before being passed on to the modifier.
Sketches can be created explicitly or implicitly. Explicitly means that a new body is created that contains the sketch. They can either be created in one of the three planes of the world space, or in the plane of a selected planar surface.
Some modifiers also implicitly generate sketches, e.g. Imprint. After selecting the face, the required sketch is automatically generated and bound to the surface, i.e. always aligned with this, even if it changes.
Sketches are edited in their own editor. As soon as this is started, the viewport changes to a two-dimensional view of the sketch plane. The grid is aligned with the sketch level and, if desired, the model is also cut in this level.
To create new segments, tools are started within the sketch editor. The segments are created by setting it's points. Existing points can be divided, this is represented by a circle around the point in question. The same thing happens when moving points. Since segments always have to form a closed curve for clean further processing, this feature is extremely important.
Constraints are used to ensure certain requirements. These can refer to points, segments or both, individually or in relation to others. A constraint solver shifts the points after each change until all constraints can be fulfilled. The solver can fail if too many constraints exist, constraints have conflicting requirements, or the numerical complexity becomes too high.
To create constraints, select all points and segments involved and select the constraint from the ribbon bar. If there is a constraint parameter, it is displayed in the property pane. In the sketch editor view, constraints are shown with white symbols on a blue background.
There are specialized programs for more complex drawing tasks. In order to be able to exchange sketches with such programs, the sketch editor has an import and export functions for several 2D vector drawing file formats. The segments are saved in nearly the same way as possible in the sketch. However, as each file format has its own data definitions, the result may vary. The same applies to the import. Constraints are not exported or imported at all.
The SVG file format has a special position here: it can be exported directly to the windows clipboard and imported again from there. This enables a quick exchange with drawing programs that also support this (e.g. Inkscape).