This Entity is Used for detecting the edge of the picture automatically. For that after loading the picture and set the reference rectangle, go to the Tools->Edge detection. Then a new window Edge Detect Image will open. You have to set the Id, where you found the maximum edge has detected, such that only the required edges are visible clearly and the unwanted objects are minimum.
After setting the Id, close the window and press trace button. To select this 'Insert Menu > Trace' or select icon from Entity toolbar. Then click on the boundary of the image and move the mouse at the boundary of the image. It will automatically detect the edge and will give make a Spline entity of the image. Click right mouse button, when you want to stop.
There is one more method to trace the edge of template. For that do the following steps.