It's the number of times you pull it down.

重要的是你拉下拉杆的次数。

耶鲁公开课 - 心理学导论课程节选

I need to make it so you can still see that, so I'm going to pull down these boards.

我需要把这块黑板拉下来,以便你们还能够看到

耶鲁公开课 - 博弈论课程节选

So if you've ever seen or used an old school typewriter, you might recall that when you're typing something out on an old mechanical typewriter, - when you like hit the char-- when you hit the enter key to move the head back to the left hand side to the next line or you would pull down some lever, it was really a two part process.

如果你们有谁曾经看过或用过老式打字机，可能还记得，当你在,这种老式打字机上打字的时候，当你-,敲入回车键，跳转到,下一行的最左边，或者,拉一下杆，这个需要两步走。

哈佛公开课 - 计算机科学课程节选