You fence the perimeter to keep out cows and people.

你用篱笆把四周围起来，把牛和人们都隔在外面。

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Couldn't I just line the perimeter of my yard with something to keep them at bay?

我不可以只用什么东西在我的院子周围画线来隔绝它们吗？

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When Bob planted a garden, he put up little hedges all around the perimeter of his yard to help keep out pests that would eat the prized vegetables he worked so hard to nurture.

鲍勃种植花园时在他的院子周围圈了一圈很小的篱笆，这样做是为了使他精心培育的名贵植物不受动物的践踏。

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One outgrowth of this kind of carelessness was the rise of opportunistic thieves who especially targeted security complexes because they know people living there were, ironically, so utterly unconscious of security once they were inside the perimeter of the keep.

CNN: Pistorius, and the psychology of walls

But after a season-long spike in goal-scoring, teams figured out that if they dropped their skaters back on defense quickly, making the middle of the ice as crowded as a Times Square subway platform, they could keep opposing players on the perimeter of the rink.

WSJ: How the Chicago Blackhawks Became Unbeatable