| 摘要 |
An extensible rule and protractor formed by an equally dimensioned pair of superposed strap members, having indicia thereon, secured together by a screw projecting through one member and sidably received by a longitudinal slot in the other member. Guide pins, on one member entering longitudinal grooves on the other member, maintain the members in longitudinal alignment when one member is sidably moved longitudinally relative to the other. A circular groove intersecting the longitudinal grooves at one end portion slidably receive the pins permitting angular rotation of one member with respect to the other to measure and define a selected angular position.
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