Auto-flop

Auto-flop is a method for automating the direction of a limb's bend, based on the movement of the Start and End Controller, when it's in IK mode. Auto-flop works by applying an expression to the limb's Clockwise property, which overrides it's normal value and links it to a new pseudo effect on the End Controller.

Autoflop demo using Nothing Up My Sleeve from the Limb Library.

When you click the + / - Auto-flop button, as well as applying the expression and pseudo effect, the Start Controller has a dynamic overlay added to it that visualizes the Auto-flop Angle and Falloff.

What to do if Auto-flop overlays are too big

Start controllers with Auto-flop have large layer bounds, so it's often a good idea to turn off Show Overlay when you're done adjusting auto-flop values. Another option is to re-size your controllers.

If Auto-flop makes your limb face the opposite of the direction you need, just invert the Clockwise value. Eg. if it was -100, change it to 100.

You can remove Auto-flop by selecting a limber layer and Option / Alt + clicking on the + / - Auto-flop button.