Sets the options for the fixed constraint to determine its behavior in a rigid body simulation. Fixed constraints keep rigid bodies in a fixed position and orientation relative to each other. This position and orientation is the state in which the rigid body is when you apply the constraint to it.
This type of constraint is useful for keeping rigid bodies attached to a platform, such as for the feet on a robot.
To create a fixed constraint: Choose Create 
Rigid Body Rigid Constraint or Multi Constraint Tool Fixed from the Simulate menu. Then pick the rigid bodies to be constrained.
To redisplay this property editor: Select the fixed constraint object and press Enter.
For more information on constraints in general, see Types of Rigid Body Constraints [ Simulation].
