In Spanish, direct objects can be replaced by direct object pronouns, which must agree in gender and number with the noun they replace.
The Spanish sentence 'El guardia de seguridad lo maneja, y te pregunta a qué hora es la fiesta' replaces the direct object 'El automóvil' with the direct object pronoun 'lo'.
When replacing direct objects with pronouns in Spanish, it is important to match the pronoun in gender and number with the noun it replaces.