| 摘要 |
A square is usable in association with a tape ruler. The square includes a ruler member as a base bar and a transverse longitudinal member formed at one side of the ruler member. An arc member is formed at the other side of the ruler member. A pair of guides are provided at the front and back surfaces of the ruler member. Each guide has two guiding grooves for receiving a respective tape ruler of different width. A permanent magnet is buried in each guide in order to maintain engagement between the guide and the tape ruler when the square is slid along the tape ruler.
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