| 摘要 |
<p>The aid has a base (10), with multiple parallel ridges which define channels (14). The ridges (12) have an inverted U-shaped cross-section and the channels have a corresponding U-shaped cross-section. The ridges have sides which bulge outwardly into adjacent channels. Card holders releasably engage the ridges or channels and are retained on them by the bulges. The holders can be slidable along the ridges, but may have projections engageable in apertures in the ridges to hold them in place. The holders can also have spigot projections to hold the cards in place.</p> |
