Learn Spanish (Latin America): A veces bajan las cajas usando el montacargas. - Sometimes they lower the boxes using the forklift.

In Spanish, the gerund (the verb form ending in -ando or -iendo) can be used all by itself to explain how or by what means an action is done. You don't need a preposition like por or con before usando; the gerund alone does the job of saying "by using".

I learned that bajar means "to go down". Why does it translate to "they lower" here?

Bajar is a versatile verb. When it doesn't have a direct object, it means "to go down" or "to get off" (like going down stairs or exiting a bus). But when it acts directly on an object—like las cajas (the boxes) in this sentence—it means "to bring down," "to take down," or "to lower."

Montacargas ends in an "s". Why does it use the singular article el?

Montacargas (forklift) is a compound word made by combining a verb (monta, from montar - to hoist/mount) and a plural noun (cargas - loads). Nouns formed this way in Spanish are almost always masculine, and they use the exact same form for singular and plural. So, el montacargas is one forklift, and los montacargas means multiple forklifts.

Could I just say con el montacargas instead of usando el montacargas?