To mirror a skeleton (Armature) in Blender:
- Create bones for one side of the rig and name them with “.L” for Left or “.R” for right.
- Select all the bones on that side.
- In Armature Edit Mode choose:
Armature > Symmetrize
Blender will create mirrored copies of all the bones with respect to the Armature origin and flip their names to names ending with the opposite side.
- When editing properly symmetrized bones,
The X-Axis Mirror tool option will simultaneously update both sides of the Armature to maintain symmetry.