| 摘要 |
<p>This invention relates to products formed of dimensionally heat-unstable plastics material. The invention is particularly useful for making preformed plastics sheet products which can be used as a covering material. The sheet material of the invention has two opposed edges, the sheet being thickened at or adjacent each of these edges in such a way as to form, when the edges are juxtaposed, an external longitudinal ridge. The disclosure includes a description of the preferred method for making the novel sheet material.</p> |
