| 摘要 |
PROBLEM TO BE SOLVED: To accumulate scums falling down from a writing face without spilling them to the surroundings and to easily remove the accumulated scums without leaving. SOLUTION: The writing face 4 on which letters and images can be written and a projected piece 9 on which a top face-opened scum accumulating channel 10 is formed are provided and regions on both end parts of the bottom face 17 of the scum accumulating channel 10 are gradually inclined in the upward direction as they approach both ends. Therefore, it is possible to accumulate the scums falling down from the writing face 4 in the scum accumulating channel 10 and to prevent them from spilling to the surroundings and when the scums in the scum accumulating channel 10 are swept up together to the end parts, as the scums can be guided to opening faces of the end part sides of the scum accumulating channel 10 along the upward bottom face 17, the scums in the scum accumulating channel 10 can be easily removed without being left.
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