Learn Spanish (Latin America): Añadir la fibra al rodillo.

In Spanish, written instructions (like manuals, recipes, or signs) frequently use the infinitive instead of a conjugated command. This creates an impersonal instruction because it doesn't address a specific person (a specific "you"), but rather just states the step that needs to be done.

If I wanted to say this directly to a coworker, how would the verb change?

If you are speaking directly to a specific person, you should drop the impersonal infinitive and use a regular imperative command. If you address your coworker informally, you would say Añade la fibra al rodillo. If you address them formally, you would use Añada.

Could I use agregar instead of añadir in this instruction?

Yes, absolutely! Agregar is a very common synonym for añadir across Latin America. In a technical manual or recipe, you might easily see Agregar la fibra al rodillo instead. It works exactly the same way.

Why is it al rodillo instead of en el rodillo if the fiber is physically going on the roller?