Locks points and curves in position.
Access Methods
Toolbar: Drafting tool set 
Parametric tool group Geometric Constraints flyout Fix Menu:
Parametric
Geometric Constraints
Fix
Summary
This command is equivalent to the Fix option in GEOMCONSTRAINT.
When you apply the Fix constraint to a point on an object, you lock the node in place. You can move the object around the locked node.
When you apply the Fix constraint to an object, the object is locked and cannot be moved.
Following are the valid constraint objects and points:
- Line
- Polyline segment
- Circle
- Arc
- Polyline arc
- Ellipse
- Spline