First of all, I'm using Carrara 5.1 Pro. So if it doesn't have this feature, may as well leave it at that... (Or you could explain it anyways, but I won't be able to use it.)

Is there a way to visually align a constraint with something? I have an aircraft model where the control surfaces do not rotate exactly about the X or Y axes, but on an axes that are an angle to those. I know that axis constraints for a mesh can have the X, Y, and Z angle number fields entered, but doing it that way is too tedious and lacks the precision I need. Trying to grab any handles that I know of rotates the object, rather than the constraint itself.

Or am I missing something obvious / doing it wrong?

 You're probably talking about the ailerons or landing gear of an imported model?

The easiest way is to open the moving part in the vertex modeling room and rotate it so that the hinge is aligned to the X axis. This probably means that you'll have to rotate the object back in the Assembly Room so that it's in correct position to the model. 

However, now that you've done these steps, if you select either Rotate or Universal Manipulator, you'll see that they now align with the X axis of the part in the Vertex Room. You can now use these tools to visually adjust to your hearts content!

Mark

Thanks! Worked like a charm.

I'm just suprised the manual doesn't cover this kind of thing better. (But then again, maybe it's not in the expected workflow?)