The picture above shows the extension jamb being applied to the sliding door frame to bring it flush with the inside drywall. The thickness of a typical finished wall is 5 3/8" thick, but most Vinyl Sliding Door frames are only 4 3/4" thick. The extension jamb product is a 3/4" X 1" rectangular Vinyl extrusion with adhesive tape on one narrow side and one wide side.

The next step is to install the door casing.

After the casing has been applied, you caulk where the casing meets the extension jamb.

The extension jamb makes it easy to bring the vinyl door frame flush with the inside wall. It can also be used on the bottom to fill the gap between the new door and carpet, tile, or wood floor.