Above are good. Podiatry Institute
P.I. Manual also has some of the bare minimums for F&A surgery (think of it as a Cliffs Notes for McGlamry since the same authors/residents made it... small like Watkins but with more F&A surgery and less biomech and general med stuff). It has good concise pearls on common workup, antibiotics, procedures, etc.
If it is any kind of historical/academic program, you also want to run a PubMed search with author filter for the program you are clerking at director and main attendings. You can just read the abstracts of the articles... even that will put you ahead of most of their clerks, and read the whole thing if the topic/procedure interests you. Some of the competitive programs will give clerks a list of recommended reading ahead of time ("classic" articles, their articles, etc), usually when you are assigned to your month and housing, etc.
I think the
ACFAS CPG are very good also... worth at least a skim to understand any standards of care stuff your pod school might have missed or you might need a reminder. Unless it's a pretty elite residency program, students honestly aren't expected to know much more than basics of surgery and to know the student class info (pharm, anatomy, etc) very well. Your Xray angles/classifications/dx and anitbiotic coverages (covered well in the CPG, esp diabetes one) are always high yield on rotations since they are just easy to ask and answer.
Have fun with externships... real fun times when my knowledge definitely increased exponentially.