An isolation tool set in the casing or liner that enables treatments to be applied to a lower interval while providing isolation from the annulus above. Cement retainers are typically used in cement squeeze or similar remedial treatments. Cement Retainers are drillable tools that can be used for squeezing cement below the retainer into existing perforations for workover, abandonment or casing repair operations. Cement retainers have a valve that can be easily opened and closed to allow for intermittent or staged squeezes.