| 摘要 |
A safety tack has a pin that is extended from a head of the tack in one state and retracted into the head in another state. The pin retracts and extends into and from the head by using a turning mechanism similar to the mechanism that allows a bolt to turn into and out of a complimentary component (e.g. a nut). By having the retracted state, the tack can be handled without injury; and by having the extended configuration, the tack can be used to tack one object to another.
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