It may not help you tie your shoe but that little plastic tip keeps the rest of the shoelace, the shoe string from unraveling into weak and useless threads.
它可能不能帮你系鞋带，但那小小的塑料头可以让鞋带的其余部分不会散开成脆弱无用的线。
2
Trevor, let me tie your shoelace.
特雷福，让我帮你把鞋带系上吧。
3
With a molecule you can't just grab hold of the ends and tie them like you would a shoelace. They're too small for that.