A structure is added by capturing a structure type (house, fence, latrine, well, etc.), a unit (m, m2, unit, etc.) and a quantity. Should you link a structure to an actual polygonal geometry, then the quantity and unit fields are automatically populated using the polygon’s size. For your information, when using rates for structures, they are based on the combination of type and unit, and multiplied by the quantity. It is also possible to provide a negotiated rate for the structure when applicable. Note that additional contextual details can be captured against a structure, including the construction date, condition, and material it is made of (wall, roof and floor).