Screening is done to ensure that nothing "falls through the cracks" during an excavation. Hopefully, all artifacts are found within the grid unit being excavated so that they can be mapped to their exact horizontal / vertical position. The screen serves as a backup if the artifact is missed.

In this process, soil which has been removed during the layer-by-layer excavations is first collected into a bucket, either using a dustpan or the trowel itself. This is dumped onto a screen mounted on a flexible platform, which is then shaken to filter out the soil.

What's left over on the screen is then examined, and anything other than normal stones, twigs, etc. is examined to determine if it's of archaeological interest or not. If so the potential artifact is bagged for later evaluation; otherwise it's discarded.

Artifacts captured in the screen are bagged for transport to the laboratory for processing. The bag has all the data associated with the excavated unit: site name, town, unit number, depth, date, excavator, quadrangle, and artifacts recovered.