שמים את ארגזי הקרטון על משטח עץ.

שמים is the present-tense plural form of the verb לשים (to put / to place).

Hebrew often leaves the subject unstated when it is clear from context or when the sentence is giving a general instruction. So שמים can mean:

• they put
• you put (in an informal instructional sense)
• people put / one puts

In practical Hebrew, this kind of sentence is very common in instructions, descriptions of procedures, and general statements.

Yes. שמים is the masculine plural present form of לשים.

A quick breakdown:

• אני שם / שמה = I put / am putting
• הוא שם = he puts
• היא שמה = she puts
• הם שמים = they put
• הן שמות = they put (feminine)

In this sentence, the plural form is used without an explicit subject, which is very natural in Hebrew.

את marks a definite direct object.

In Hebrew, you usually use את before the direct object when that object is definite, for example:

• a noun with ה־
• a name
• a possessive noun
• a construct phrase that is definite

Here, ארגזי הקרטון is definite, so Hebrew uses את.

Important: את is not translated into English. It is just a grammatical marker.

Because ארגזי הקרטון is a construct chain.

The basic plural is:

• ארגזים = boxes

But when that noun is linked to another noun after it, Hebrew often changes it into the construct form:

• ארגזי = boxes of ...

So:

• ארגזים = boxes
• ארגזי הקרטון = the cardboard boxes / the boxes of the cardboard

This is a very common Hebrew pattern.

A construct chain is a noun + noun structure that often corresponds to English X of Y or sometimes an adjective-like phrase.

So:

• ארגזי הקרטון literally looks like boxes of the cardboard
• in natural English, this becomes the cardboard boxes

The first noun changes form because it is attached to the second noun.

Other examples:

• בית ספר = school, literally house of book
• בקבוק מים = water bottle, literally bottle of water

Hebrew uses this structure a lot where English might use either of or an adjective.

Because קרטון here is definite: the cardboard.

In a construct chain, the definiteness of the whole phrase is usually determined by the last noun. So because it is הקרטון, the whole phrase ארגזי הקרטון becomes definite.

That is why the sentence also uses את before it.

Compare:

• ארגזי קרטון = cardboard boxes / boxes of cardboard (indefinite)
• ארגזי הקרטון = the cardboard boxes (definite)

That is normal in Hebrew construct chains.

In a construct chain, the first noun usually does not take ה־, even when the whole phrase is definite. The definiteness is shown on the last noun.

So Hebrew says:

• ארגזי הקרטון

not:

• הארגזי הקרטון

This is one of the key things to learn about the construct state: the definiteness shows up at the end, but it affects the whole phrase.

Because משטח עץ is indefinite here.

• משטח = surface / platform
• משטח עץ = a wooden surface / a wood surface

Since there is no ה־ on the phrase, it is understood as indefinite.

Compare:

• על משטח עץ = on a wooden surface
• על משטח העץ = on the wooden surface
• על משטח עץ גדול = on a large wooden surface

So the sentence is talking about placing the boxes onto a wooden surface, not necessarily a specific previously mentioned one.

Hebrew often uses a noun + noun structure where English uses an adjective.

So:

• משטח עץ = wood surface / wooden surface
• literally: surface of wood

This is very natural in Hebrew.

Another common example:

• שולחן עץ = wooden table
• literally: table of wood

Hebrew can also use adjectives in many places, but for materials, the noun-noun structure is extremely common.

על means on / onto / upon, depending on context.

In this sentence it marks the location or destination of the placing action:

• שמים ... על משטח עץ = put ... on a wooden surface

It is one of the most common Hebrew prepositions.

Yes, Hebrew word order is somewhat flexible, but this sentence uses a very normal and neutral order:

• שמים = verb
• את ארגזי הקרטון = direct object
• על משטח עץ = prepositional phrase

You may also hear other orders in speech for emphasis, but the given version is standard and natural.

Good question, because the spelling can look confusing without vowel marks.

• שמים as a form of לשים means putting / put
• שמים as sky / heavens is a different word, usually pronounced shamayim

Context tells you which one it is. In this sentence, שמים את... על... clearly has the structure of a verb followed by a direct object, so it must mean put.

So here, שמים is the verb, not the noun sky.