| 摘要 |
A base has a horizontal top face with an aperture, a bottom face, a central vertical support with projections extending from each end. The projection of the bottom end is coupled with the central aperture of the base. A knob assembly has a lower portion with guide posts, a braking section and a downwardly projecting member with a recess with grooves. Between the upper and lower portions is a coil spring.
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