Erasing 

Here are a set of tools for removing drawings from the screen. 

The Undo Button removes the last thing you drew. There is no actual limitation on how far back you can “undo.” If you draw something new, anything “undone” may not be recovered with Re-do. 

Clicking the Re-Do Button will bring the most recently undone object back again. You may continue to click Re-do until everything “undone” has been brought back.

The Clear Button removes all drawing from the video screen. Clear may also be reversed and re-done with the Undo and Re-do functions. When in Compare mode, the Clear button will clear only the selected side of the video window.

Although not recommended for use, there is also an Erase tool, which operates like a pencil eraser. Select the Freehand tool then use either the right-mouse button or the flip-side of a drawing tablet pen.