Archaeologists must be very careful when they start working on a "dig". It's important to know where an object was found and what was found near it. This helps archaeologists date an object.
The first thing that is done is to prepare a grid. A grid is a design that breaks a section of ground into small squares. These squares are marked usually with rope and string.
Each little square in the grid has to be carefully searched and measured. If something is found, archaeologists note how deep in the earth it was. It is most important to carefully label each item by assigning it a number in the grid. Archaeologists want to be as accurate as possible.