There is a knack in tying ropes together.

把绳子绑在一起有点技巧。

He has a knack of saying funny things.

他有说俏皮话的本事。

He has a knack of doing stupid things.

他蠢事。

Making omelets isn’t difficult, but there’s a knack to it.

煎蛋饼并不难，但有窍门。

There is a knack in it.

这里面有点窍门。