You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Pub

Context:
As many pubs are centuries old, many of their early customers were unable to read, and pictorial signs could be readily recognised when lettering and words could not be read.

Question:
What type of pub signs were useful to an illiterate clientele?

pictorial signs