Why did this seem familiar? It came back to me:

In early '73, at Fort Sam Houston in San Antonio, I finished corpsman school but then had a 3-week wait for an advanced school at Fort Sam to begin. So, for 3 weeks, we were obliged to report to the "casual pool" where different units at Fort Sam could drive by and pick up some number of "casuals" to perform complicated tasks like raking leaves, mowing lawns, or painting rocks.