Exercise book for vocabulary learning uses page extensions folding over onto columns so inbuilt rail piece forms transparent pocket for opaque cover strip to obscure respective columns

摘要

The columns (5-8) of the contents pages (3,2) can be covered over as required as part of the exercise book, notably extension (9,10) of the pages which can be folded over into the page so the outer columns (5) or (8) are covered over, using a rail piece (13) fitted into the back spiral (4). Opaque strips (15) can be slid into top or bottom ends of the transparent pockets (14) of the rail piece. One column per page (2,3) should be color-backed.