Curling accrues on the front edge of the siding drip edge. As the siding is exposed to substantial moisture it expands and can cause the front edge to separate from the layers inside a piece of siding. Once a piece of siding has curled the only way to try and make it look uniform again is to remove the curled edge. Removing the damaged edge exposes the siding and will void any warrantee that may remain on the siding. A razor knife or sanding is the best way to remove the edge. Scraping will cause further damage and create a rough edge on the siding. Once the edge is removed it is essential that proper preparation is applied to protect the exposed areas.