For optical mark reading, the scanned image must have some special reference points that mark the beginning and end of the sheet. Corners of the OMR Sheet are most important. There are some special marks at measured distances on OMR Sheet which are critical to accurate reading of the OMR Sheets. The software follows these markers to identify the required bubble at the referenced location. So these markers are realIy important. If we punch, tie, staple or pin the OMR Sheets we might create disturbance in the reading path of OMR Sheet Reader Software.