Abstract: A medical lancing device including a clam-shell housing that holds a replaceable multi-lancet cartridge. A control mechanism includes a linear-pull slider that is moved in and out to operate various mechanisms of the device. An interlock mechanism includes at least one rib on the slider that engages at least one finger on the housing to lock the housing closed when the slider is in a retracted or only partially extended position. And the interlock mechanism includes at least one void on the slider that aligns with at least one finger on the housing to permit the housing to be opened when the slider is in a fully extended position.