Each line is a single, simple unit. It contains one idea, and one alone.
No two lines should ever describe the same thing.
You can use a multitude of different words to describe the same picture. In fact, that's precisely what makes writing an art form. But it's a double-edged sword when we trick ourselves into describing the same work experience in different ways, on separate lines.
Each line should plant a clear, distinct picture in the reader’s mind, and then allow them to move on to the next idea.
If bleed your statements together, your reader will experience déjà vu and become confused. They will trip on your redundancy.
A line has one job: make the point, and pass the baton to the next line.
See what I did there? Two of the last three lines effectively said the same thing. I catch myself doing this all the time. In some art forms, this is done on purpose; saying the same thing in different terms can help illuminate the meaning of an idea.
But this is rarely what you want on a resume. If you take multiple lines to express a single idea, you're abusing the whole purpose of the document.
See if you can find a way to clean up these next 2 bullet points, which appear one above the other on an executive assistant's resume:
Managed reception area, greeting visitors and coordinating telephone and in-person meetings on behalf of the CEO.
Organized travel and managed meetings for all C-level executives.
If you read both lines together and were given 5 seconds to recall them from memory and summarize them, would you need 2 sentences, or just one?
We can easily condense the meetings logistics into a single line that packs more punch and provides better detail:
Managed calendar, correspondence, and travel for CEO and the executive team.
Go through your resume and see how many lines you can merge succinctly. You might be surprised by how many you find.
Once you've got each line standing firmly in its niche, it will be ready for the line test.