Final answer:
The quote in question uses a metaphor by comparing the act of overindulgence to 'making pigs of ourselves'. The metaphor serves to illustrate the excess without a literal transformation into pigs.
Step-by-step explanation:
The quote "We'd made pigs of ourselves. Now we wanted nothing more than to take a nap in the afternoon heat" (McCall 132) is an example of a metaphor. A metaphor is a figure of speech that implies a comparison between two unlike things by stating that one thing is another. In this case, the phrase "made pigs of ourselves" doesn't mean that the individuals literally turned into pigs, but is used to convey the idea that they indulged excessively, akin to the way pigs are often stereotypically considered to overeat. The latter part of the quote establishes the consequence of their overindulgence, which is a desire to sleep, but this is not a figure of speech; it's a literal desire following the excessive eating.