盖 (gài) is a verb meaning 'to cover,' 'to lid,' or 'to build.' It can describe placing a cover on something, stamping a seal, or constructing a building. As a noun, it also means 'lid' or 'cover.'
出门前记得盖上锅盖。
chūmén qián jìde gài shàng guōgài.
Remember to put the lid on the pot before you go out.
他们打算在村子里盖一栋新房子。
tāmen dǎsuàn zài cūnzi lǐ gài yī dòng xīn fángzi.
They plan to build a new house in the village.
请在这份文件上盖个章。
qǐng zài zhè fèn wénjiàn shàng gài gè zhāng.
Please stamp this document.