If you have a full joints skeleton in Maya then you deleted the left side of the am joints – for example – now you want to mirror the right side to the left side, if you do it with the traditional way, Maya will simply crash down.
So How can you do it ?? simple watch my video

if you have any questions, problems, feedback Please

- Create a simple object as trend unit like this one.

- Adjust the pivot point and put it where it should rotate.