| 摘要 |
A ruler has a base, a design paper and a cover. The base has a ridge, a first inclined sheet, a second inclined sheet, a first horizontal tab and a second horizontal tab. The first inclined sheet is formed on the ridge. The first horizontal tab is formed on the first inclined sheet and has a top surface and multiple scales. The scales are formed on the top surface or the bottom surface. The second inclined sheet is formed on the ridge. The second horizontal tab is formed on the second inclined sheet. The design paper is mounted on the base. The cover is transparent, is mounted detachably on the base and covers the design paper. The design of the ruler can be replaced and the scales are not abraded easily.
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