By default when you hold the Alt key and left click and drag in the canvas, you’ll create a bone.  There are actually two other types of objects you can create via this method which aren’t used for animation, but instead are for game-play related information.  One of these two objects is collision rectangles.  Collision rectangles can be used by a game engine to designate the actual areas the game will detect collisions with.  For example, durring a punch animation, you can create a collision rectangle to designate the area of the animation (near the fist) which the game would use to see if the punch makes contact with enemies in the game.  You could also use collision rectangles to designate regions of the body which would take diferent amounts of damage from attacks, or would trigger diferent reactions if collidded with. To create Collision rectangles, do the following:
Adding Collision Rectangles to Frames
1) Left click on the Currently Equipped Tool type at the top of the Palette located near the top right of your screen, and select “create box”
2) Make sure you’re at the point in the timeline (or keyframe) you want the collision rectangle to exist, then hold the Alt key and left click and drag on the canvas to create your collision rectangle. You can then copy and paste it to other keyframes, or use the paste to all keyframes option to propagate the Collision rectangles across the entire animation.
3) Once in place, if left click, thransform gizmo’s appear so the rectangle can be stretched, rotated, and have its pivot point changed just like images(sprites) can.  These diference will be tweened between keyframes which include the same collision rectangle!
4) By double-clicking on the name of the rectangle in the Z-order palette, you can give it any name youd like for easy recognition of the rectangles purpose.