A weir with locks is used to encompass a platen used for chemical-mechanical polishing. The weir retains slurry that would otherwise be flung from a rotating platen because of centrifugal force. However, the locks permit some slurry to leave the platen, which enables the polishing process to include desirable flows of fresh slurry through the polishing pad to replenish polishing components and to flush out deleterious waste products. Additionally, the effective orifice size of the locks may be made a function of platen rotation rate. Polishing processes are possible in which the depth of the polishing slurry on the platen is a function of platen rotation rate.