"captive washer" is a type of washer

帅哥

  "Screws with captive washers thread easily to save installation time." \]=''C=J  
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   "Remove the cover by unscrewing the four side screws, which have captivated washers." ]u<8j r  
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"Others prefer a bolt with a large captive washer such as the ones shown." *P0sl( &  

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  "The factory bolts have a locking feature built into the retained washer."  8qF OO3c\V  
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这样容易说明白些 ，呵呵