Learn French: Le douanier laisse passer l'homme à la douane. - The customs officer lets the man pass at customs.

When you use laisser (to let or allow) followed by an infinitive verb, the two verbs usually stick together. Unlike English, where we put the person doing the action in the middle ('lets the man pass'), French groups the verbs and places the noun after them: laisse passer l'homme.

If I wanted to say 'lets him pass' using a pronoun, where would it go?

The object pronoun goes right before the verb laisser. You would say Le douanier le laisse passer. With the laisser + infinitive structure, object pronouns are almost always placed before laisser, not between the two verbs.

What is the difference between le douanier and la douane?

La douane is the location or institution of 'customs' at a border. Le douanier is the person who works there, the customs officer. The -ier suffix is commonly used in French to indicate a profession, just like in le policier (the police officer).

Why do we use à la in à la douane?

Douane is a feminine noun, so it uses the article la. To say 'at' a specific place, institution, or checkpoint, French uses the preposition à, which gives us à la douane.