IK Handle as Lock
Did you know an IK handle can be used as a lock? Correction: IK handle is used as a lock assistant to improve the quality of a full lock.
The ik handle must be set with IK interpolation, Firm handle and Lock children.
Just found out that a lock is needed during the animation process. So as shown it’s good for playback but for animation the ik handle “lock” also needs a regular lock. The lock isn’t associated with the “ik handle lock” it’s just there in addition to it. So you do regular rig then add the special ik handle. Hope that makes sense.
Scaling a full lock will make the skeleton blow up.
Scaling position and rotation seems ok.
Handle and lock positioning
I believe it’s better to place handles at joints and locks on bones. The placement is more intuitive and it may be important when setting several handles on one joint. The image shows that clicking a joint centers the handle on the joint. If you click a bone then the handle is not centered where you click. If you click a bone to add a lock the lock appears on or near the bone. If you click a joint when adding a lock the lock will move to the center of a bone (the bone up the hierarchy?) .
EDIT: I change my mind about locks always going on bones. Position locks might be better in some cases on the joint instead of the bone and when you click to add them to a joint they are added at that location. This is what IK Handel does in his videos.
Multiple IK handles can be assigned to a joint.
Align Inverse Kinematics handle tool. Use it to make a handle follow a bone when it rotates instead of the default of just following the whole skeleton when it rotates.
IK Handle defaults are set for FK. An IK default is better for an IK handle so turn off Posing only and move the FK/IK Interpolation slider all the way to IK.