A slump cone is a truncated metal or plastic cone used in the concrete slump test, a crucial field test to measure the workability, consistency, and water content of fresh concrete on construction sites. The test involves filling the cone with concrete in layers, tamping it, and then lifting the cone to see how much the concrete "slumps" or settles; the measured height difference indicates its consistency, with a higher slump meaning wetter, more workable concrete.