A gap in the fence is a magnet is a form of figurative language describing what gaps in fences are.
I think it means to have hard boat shells meaning hard sides as in something that is hard and wont brake and will last in strong storms for a period of time.
When your search something online, and a web page is displayed, you can find the text that you want by using a keyboard shortcut. This keyboard shortcut would be CTRL + F, wherein it instantly locates the keyword you want in order for a fast and more efficient researching.
For what book and what does the line say?
