| 摘要 |
The device has a frame (1) with four sides at right angles with mitred joints. Each side has a skin (2) of plywood which is glued to a frame running lengthwise (3) which is less wide than the strip of plywood and which is made of two planks which are stuck together (3a, 3b). The strip of plywood is less than 20 millimetres thick. The planks (3a, 3b) are positioned with their grain running the same direction towards the centre of the frame (1). The plywood and the lengthwise frame (3) are centred in relation to each other so the plywood extends an equal distance on either side of the frame. The opposite faces (2b, 2c) of the plywood which will be held between the form panels have a watertight seal (5, 7).
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