Slot

Slots are parts controlled by bones. A slot must be and can only be controlled by one bone. The translation, rotation, and scaling of a bone will drive the changes in the slot's translation, rotation, and scaling.
A slot is a container that can hold one or more slot resources, but only one slot resource can be displayed at any given moment.
Slot properties include: position, angle, scale, color, transparency, and display object.
Among them, position, angle, and scale are relative to its bone.
Color and transparency only affect certain slot resources.
Display object indicates which slot resource is currently displayed by the slot.