有时候，我们想用一个动词来形容一个名词。为了表示它形容名词的功能，我们一般可以加 ing 或者 ed 。这样可以把形容动作的动词和形容名词的动词分清楚。所以我们可以看得出来，这里的 sticking 是形容钉子的位置，而不是钉子的动作。同样的，jutting 是形容石头的位置。 stick 和 jut 本来是表示动作的。打个例子，he always sticks out his hand to ask for money. 他老是把手伸出来球人给他钱。 我从词典看到了这句话，觉得很好用。His mouth started to jut out, and his jaw got longer. 他的嘴向前突出, 下巴也变长了.

现在分词作定语。Present participle used as an attribute. I didn't notice that there was a nail sticking out of... = I didn't notice that there was a nail which stuck out of... There was a hug rock jutting out over the cliff = There was a hug rock which jutted out over the cliff

很容易理解，there is something (that was) doing ... 这里是现在分词表示状态，补足语，补充说明nail的当时的情况是怎么样的