A method for mounting a functional element of a washing fluid reservoir on a corresponding fixing portion of a structural component of a motor vehicle, wherein the fixing portion is at least partially made of a plastics material and wherein an opening is formed in the fixing portion, comprising, for arrangement in a final installation position:
- inserting an insertion portion of the functional element into the opening, and
- sliding and/or rotating the insertion portion in a direction transverse to a depth direction of the opening,
- such that the functional element in the final installation position, viewed in the depth direction of the opening, is fixed positively with respect to the structural component.