You can use Alt G, Alt R and Alt S to clear the Translation, Rotation and Scale back to 0,0,0 for the selected controls.
If you have automatic keying, it will keyframe this for you. If you don’t have auto keying turned on, it will just change the values to 0,0,0 but if you want it to stay there, you need to key it before moving onto a different frame (otherwise it will snap back to the position that the Graph Editor tells it to).
The connected black and yellow bars are to show that there is no change in value between these keyframes. ie – it is held.
The black means it is not selected, the yellow means it is selected.
Hope that helps.
