I'm trying to get data on commute methods for an area using American Community Survey 2015 table B08505A, but as you can see in this table describing geographic restrictions for ACS data: https://www2.census.gov/programs-surveys/acs/summary_file/2015/documentation/tech_docs/ACS_2015_SF_5YR_Appendices.xls The data is reported for "Place of Work Only". What does "Place of Work Only" mean in terms of US census geographic restrictions? I can't find info on this anywhere.
This means that it was collected with reference to where the respondent works and not where the respondent lives.
The PDF called "2016 Subject Definitions" provides the description that you are looking for. From the PDF currently found at this link: https://www2.census.gov/programs-surveys/acs/tech_docs/subject_definitions/2016_ACSSubjectDefinitions.pdf
From the Section called Journey to Work on Page 92: "Data on place of work refer to the geographic location at which workers carried out their occupational activities during the reference week."