| 摘要 |
A blackboard is arranged to have on its sides separate blackboard units folded in layers for showing particular study materials. The units are folded on hinges for the separate unit to swing-open to be held on to the main board frame by magnets and iron fixtures. A frame (11) of a blackboard (1) is provided on both the side ends with separate auxiliary frames (12,13) each for holding a set of unit boards (2,3,4,5) in folding. The main board (1) and the units have respective magnets and iron fixtures (8) for holding the units on the main frame (11).
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