You can define objects as parallel in assembly by using Parallel function in the “Assembly constraints”.,
To create Parallel constraint
- Start the “Assembly constraints” command.
- Set the constraint type as “Parallel”
- Select the first planar object of a part in an assembly
- Select the second planar object in another part in an assembly.
- To change the direction of the objects click the reverse icon in the “Geometry to Constrain” tab. (The first object direction will change. The second part stays on its current location)
- Click “Ok” to finish command.