I have assembled many 1:20K BC TRIM sheets. These are layers provided by the Government of British Columbia that include lakes, forested areas, glaciers etc. Data is sheet based and I have joined 29 sheets. I used the dissolve command to join internal polylines together for conversion to polygons (such as lakes). How do I treat the edge polylines. These are the lakes etc that are around the outside boundry of my merged sheets. How do I close all would be polygons at the edge. I tried creating a mask layer and merging, but I still don`t know how to close the lakes etc. It must be in spatial join, but I just can`t see the solution. I have many layers to convert and it is very time consuming to do it manually. I have the ArcView level of ArcGIS.