Subject + 塞 + Object + (Location)
The verb 塞 (sāi) means "to stop up," "to stuff," or "to squeeze into," describing the action of filling or blocking a space with something. It can also be pronounced sè when used in compounds meaning "to block" (as in 堵塞). This verb is very physical and concrete, often describing cramming objects into tight spaces.
她把衣服塞进了已经满了的行李箱。
tā bǎ yīfu sāi jìn le yǐjīng mǎn le de xíngli xiāng.
She stuffed the clothes into the already full suitcase.
别把纸塞在沙发缝里,快拿出来。
bié bǎ zhǐ sāi zài shāfā fèng lǐ, kuài ná chūlái.
Don't stuff paper into the sofa cushion crevice — take it out now.
他随手把钥匙塞进了口袋里。
tā suíshǒu bǎ yàoshi sāi jìn le kǒudài lǐ.
He casually stuffed the key into his pocket.