Double aluminum blanks are used with lapping films for sharpening knives using Hapstone or Edge Pro knife sharpeners.
PSA-backed (pressure sensitive adhesive) lapping film is extremely easy to use. Simply peel off the paper backing and press it down on the blank. Avoid getting air bubbles between the film and the blank.
To apply non-adhesive lapping film, use double-sided adhesive tape or acrylic glue.