Reserve is a unit or a leeway for unplanned situations. It prevents the project delays and adjust the deviating results with the objects. It provides more money and time, but also a quick access to the technical reserves to correct a mistake. There are temporal, financial and qualitative reserves for the risks in the project planning. They are assigned to the whole project or to the project phase or individual work packages.
The mile stones are the temporal reserves in the Gantt chart, which can display the critical path. Another reason is multiplication mistake in the Gantt chart. The temporal reserves are often called dummy position in the project planning, with other words, time reserve. The qualitative reserves represent something different. If the customer is not satisfied with the project results or with the additional financial effort for the improvement, the project management has already a solution. Such an approach leads to the further good cooperation.