| 摘要 |
An extrusion ( 10 ) including a central wall portion ( 12 ) and a surrounding perimeter portion ( 14, 18 ) whereby the central wall portion ( 12 ) divides the extrusion ( 10 ) into opposing chambers, said perimeter portion ( 14, 18 ) having a respective opening therein into each of said chambers and each said chamber being able to have a perimeter portion ( 14, 18 ) of a further extrusion ( 10 ) locked thereinto to form an interlocked unit.
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