Using Fezzik's Reduced Row Echelon Form, we show how each RREF is constructed of an identity matrix $\mathbf{I}$ in the pivot columns and a free column matrix $\mathbf{F}$. From there, we can see how a matrix $\mathbf{N}$ can be built that contains a set of null vectors, a basis for Nullspace (everything you need to know about bases is coming up soon).