Rubber face loose. Scrape off glue and apply rubber cement to back of rubber and to wood. Let dry. Apply a second coat to one surface and smooth rubber down.
Cork face loose. Scrape off glue and reglue with Elmer's Glue-All.
Sandpaper face loose, damaged. If face is simply loose, scrape off old glue and reglue with Elmer's Glue-All. If paper is damaged, peel it off completely (wetting the surface will help). Stick down new sandpaper with rubber cement.