  Most, if not all, physics undergraduate degree programs include instructional
lab experiences. Physics lab instructors, both faculty and staff, are
instrumental to student learning in instructional physics labs. However, the
faculty-staff dichotomy belies the complex, varied, and multifaceted landscape
of positions that lab instructors hold in the fabrics of physics departments.
Here we present the results of a mixed methods study of the people who teach
instructional labs and their professional contexts. Recruiting physics lab
instructors across the US, we collected 84 survey responses and conducted 12
in-depth interviews about their job characteristics, professional identities,
resources, and experiences. Our investigation reveals that lab instructors vary
in terms of their official titles, job descriptions, formal duties, personal
agency, and access to resources. We also identified common themes around the
value of instructional labs, mismatched job descriptions, and a broad set of
necessary skills and expertise. Our results suggest that instructors often
occupy overlapping roles that fall in between more canonical jobs in physics
departments. By understanding the professional contexts of physics lab
instructors, the rest of the physics community can better promote and engage
with their critical work, improving laboratory learning both for students and
for the lab instructors who teach and support them.
