Running water is never stale and a door-hinge never gets worm-eaten.

流水不腐，户枢不蠹。

《新英汉大辞典》

"Running water is never stale and a door-hinge is never worm-eaten" means that constant motion prevents the inroads of germs and other organisms.

“流水不腐，户枢不蠹”，是说它们在不停的运动中抵抗了微生物或其他生物的侵蚀。

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ZMC Products Co. , Ltd. Professional production of the entire buffer out of 45 slides, 45 buffer slide, slide damper, Door stopper, Door Holder, furniture, concealed hinges, hinge.

佛山市顺德区制美五金制品有限公司专业生产全拉出45缓冲滑轨、45缓冲滑轨、滑轨阻尼器、门吸、门碰、家具暗铰链，合页。

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One neat trick: The right-side passenger door can hinge conventionally or backward, so people getting into the back of the car have easier access.

FORBES: Vehicles Feature

Opening the rear door reveals a rear-hinged configuration, with a single, oversized, brushed-aluminum hinge articulating diagonally from the rear door cutline.

ENGADGET: Hyundai unveils HCD-14 Genesis concept: suicide doors, gesture and eye controls