  We show that it needs a more delicate potential to confine particles inside a
well. The original model containing a vague notation of infinity in the
potential energy is ambiguous. Using the Heaviside step function and the Dirac
delta-function, we give a precise form for the confining potential. Although
such form appears unusual, the ambiguities are resolved. This form also shows
that the infinite square well is not the limit of a finite square well.
