He gives the example of how a carpenter will often know that a nail works better in certain situations and screw better in others.
他用了这样一个例子：木匠通常是怎么知道在什么情况下用直钉，什么情况下用螺钉的。
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"The rollercoaster is wooden and so unlike rides made from iron and steel there was always a chance of the odd nail or screw that would not be entirely flat," he said.
Numerous studies have been published regarding the comparison between intramedullary nail and the dynamic hip screw and plate for the fixation of intertrochanteric fractures in elderly patients.