Comment by BizarroLand

A patent on a widget does not prevent me from building that exact widget.

In fact, a good patent will tell me exactly how to make that widget.

All a patent does is prevent me from building and selling that widget without getting permission from the patent holder, and even then, the patent holder has to discover that I am selling their widgets and possibly sue me to stop me or extract their fair portion of the proceeds if I do not agree to a preliminary settlement.