The most basic form of design for manufacture as it applies to PCBs is the use design rules and design rule checking in PCB design software. Design rule checking (DRC) is the process of looking at a design to see if it conforms to the manufacturing capabilities of a PCB fabricator. Typically the designer will get the highest tolerances that a PCB fabricator supports from the fabricator, load these tolerances into their design program and then run a design rule test on their prospective design. Design rule checks are commonly integrated into PCB design software and are not typically considered as add on service. More advanced design for manufacture analysis software is also available to look for more complex and less obvious design flaws. Typically, DFM software checking is offered by PCB fabricators to customers as an extra service. The reason for this distinction is because of the plus cost of high end DFM software and the additional training required for using it.