"he made several studies before starting to paint"
"sketch the building"
"sketch the outline of the book"
"outline his ideas"
He sketched in the details.
他把细节勾勒了进去。
I don't quite understand; can you sketch in a few details of what you're suggesting?
我还不太明白,你能否把你的建议说得具体一点呢?
Sketch out what you intend to do.
简述一下你准备做的事情。
The teacher sketched out the main point of the article.
老师扼要地叙述了文章的要点。