You can use the Dimension
option 
to produce a fully defined sketch, which defines
the dimensions of all entities with no degrees of freedom left unresolved.
You can also use the Add Constraints
option 
to
eliminate degrees of freedom.
Note:
You can press the ALT Key to draw
a free sketch displaying only end point constraints, or alternatively,
select the Skip all constraints
checkbox in the Constraints dialog,
displayed by clicking the Constraints
Filter 
icon from the Sketcher
Toolbar.
The colors of the dimensions and entities will tell you if the sketch is:
Dimensions appear in magenta when they are added. If any part of the sketch remains blue, the sketch needs additional dimensions to be considered fully constrained. In the case below, either a line length or angle must be added.
While the sketch is under-constrained, the following message will appear in the bottom section of the display:
When all dimensions and entities appear in magenta, the sketch is fully defined. In the case below, the location of the triangle with respect to the origin, as well as all lengths and angles, are known.
While the sketch is fully constrained, the following message will appear in the bottom section of the display:
If too many dimensions are applied, the entities that are over-constrained, as well as their dimensions, appear in orange.
In the example below, sides 1 and 2 of the triangle, as well as the angle between them, are dimensioned. This causes the entities to be over-constrained.
To bring the entities back into a fully constrained condition, you must delete one of the dimensions, as follows:
Click the Trim
option 
, and click on a dimension to delete it. (To avoid
unintended deletions, remember to de-select the Trim
option.)
Click the Select option 
, select the dimension and press Delete on the keyboard.
Geometric Inconsistency or Impossibility
If constraints or dimensions are applied that make it impossible to find a geometric solution for the sketch, the entities and appear in red.
In the example below, the bottom leg of the triangle was assigned a dimension so large that no geometric solution exists. The problematic dimension is underlined.
To bring the entities back into a fully constrained condition, you must delete or modify the problematic dimension, as follows:
Click the Trim
option , and click on a dimension to delete it. (To avoid
unintended deletions, remember to de-select the Trim
option.)
Click the Select option , select the dimension and press Delete on the keyboard.