Nǐ / xiān / bǎ / lā / liàn / lā / hǎo / Tiān / ān / mén / kāi / le / hěn / róng / yì / bèi / rén / kàn / jiàn

你先把拉链拉好，天安门开了很容易被人看见。

Zip up first; if your fly is open, people can easily see it.