We propose a method to produce a definite number of ground-state atoms by adiabatic reduction of the
depth of a potential well that confines a degenerate Bose gas with repulsive interactions. Using a variety of
methods, we map out the maximum number of particles that can be supported by the well as a function of
the well depth and interaction strength, covering the limiting case of a Tonks gas as well as the mean-field
regime. We also estimate the time scales for adiabaticity and discuss the recent observation of atomic
number squeezing [Chuu et al., Phys. Rev. Lett. 95, 260403 (2005)].