While they were generally used in a transfer service, they were also used for short local runs.
As a child, I remember seeing them on GM&O trains in my cousins hometown of Centerville Al, on short locals from Tuscaloosa to Maplesville. I also occasionally saw them on the SRR out of my hometown of Selma, Al. I never saw them run in true transfer service, even in my hometown, which had 4 RR's servicing the town. There was the SRR yard, and then the combined L&N, WofA, and GARR yard. The yards were less than 1.5 miles apart, and "transfers" consisted of parking cuts of cars on a SRR siding, that ended near where the L&N/WofA/GARR yard began.