重い箱を

a heavy box

→ 重い
phrase Rare #37,798
a heavy box 重い means “heavy,” 箱 means “box,” and を marks the phrase as the direct object of the verb. The phrase usually appears as part of a longer sentence.
JA: 重い箱を運ぶのを手伝ってください。
EN: Please help me carry this heavy box.

体調が悪くなっているので生憎そんなに重い箱を運ぶことはできない

Unfortunately, I can't carry such a heavy box because I'm not feeling well.

彼は棚から重い箱を降ろした

He took the heavy box down from the shelf.

その彼女は重い箱を片手で持ち上げた

She lifted the heavy box with one hand.

その男の子は重い箱を片手で持ち上げた

The boy lifted the heavy box with one hand.