Once digging begins, the process is slow and methodical. A site is usually overlaid with a grid of crisscrossing strings, creating a coordinate system that makes it easy to map the site. Workers (often volunteers) clear the dirt in each square, going down a few inches at a time. As they dig, they begin to notice changes in the soil types, which indicate successive levels of use or occupation—floors of houses, dirt laid down by wind or floods, ash from fires. By carefully recording the depth of the objects, as well as their horizontal locations, the finds can be mapped accurately in three-dimensional space. This type of record-keeping becomes crucial in the later dating and interpretation of the site. Since excavation actually destroys an archaeological site, detailed field notes and photographs of the objects in situ are also produced. Archaeologists want to be able to reconstruct on paper the entire site and the location of all architecture and artifacts.
Depending on the type of soil, level of excavation, and goals of the dig, workers might use anything from bulldozers to picks and shovels to trowels to brushes and dental tools. Most often, they carefully scrape the surface with the side of a trowel. They scoop the soil into buckets and, after separating out the visible artifacts, sift it through a screen to make sure nothing has been missed.