Bend the skin over the edge of a table, and glue the edge. Be careful not to get any glue outside of the edge. It makes it hard to sand. I prefer old fashioned Ambroid. Makes the seam easier to final sand. Some skip this process and feel that the Polyurethane glue used to glue the skins to the cores will foam up through the seams. This is true, however, I find the seams a lot harder to sand compared to the Ambroid. So in effect, I am using the Ambroid to seal the seam from the Polyurethane.