Click the Features | Edit Polylines | Connect Polylines command or right-click on the selection and click Connect Polylines to connect selected polylines and spline polylines. The polylines are connected at the closest endpoints on each line. For the command to be available, two or more polylines or spline polylines must be selected.
The new polyline retains the line properties from the polyline at the bottom of the Contents window. If the object name has not been changed from the default Polyline, the object is renamed Polyline. If the object name had been altered, the custom object name from the bottom polyline is retained.
If objects should be edited in a base map, click on the object in the Base layer to select it. Click the Features | Group | Start Editing command to enter editing mode. Then, click the Features | Edit Polylines | Connect Polylines command. The polylines are connected. Click the Features | Group | Stop Editing to end object editing mode in the base map.
Polyline to Polygon
Polygon to Polyline