求翻译：材料表中,所选用规格不得任意替换,若备料确有困难时,须经设计单位同意,制作前，构件须1：1大样进行核对，尺寸无误后方可加工。是什么意思？

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Materials List, the selected Specifications shall be subject to arbitrary replacement are stocked up, and if there are difficulties, when consent shall be subject to the design, production units, components before the same shall be 1:1 matching, size and unmistakable rear can be processed.

In the bill of materials, selects the specification not to have to replace willfully, when prepares materials really has the difficulty, must pass through the designing department to agree, before the manufacture, the component must 1:1 detail drawing carry on the checkup unmistakably, after the siz

Material table, selected specifications shall not be any replacement, if the stock does have difficulties, shall be agreed by the design unit, before making, component 1:1 check detail, the size is correct only after processing.

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