Flagging data is allowed in only some plot classes (point, bg, and scan), and manual flagging only if the plot window contains a single plot (remember to use the ALL IN 1 option to plot a selection of data into one plot). Automatic flagging is recommended only for point data. In the manual mode, you will define a box on the plot by first clicking the left mouse button on the upper left corner, then set the size/shape of the box by moving the cursor and clicking the middle button, then positioning the box. Click on the left button to place another box, or the right button to finish. Finally you will be presented with a list of options of what to do with the boxed data. Flagged data will be colored red.