an optical reagent format with a precise capillary channel is made by molding a format on a carrier of a precise predetermined thickness . the carrier includes an insert at least a portion of which is molded in the format . once the format is made , the insert is detached from the carrier and removed from the format leaving a precisely dimensioned capillary channel with an inlet and vent . a reagent may be applied in the capillary channel and the format used to measure the analyte in a fluid such as blood . an electrochemical sensor with a capillary channel is formed by placing a sacrificial insert and electrodes on a sensor base and applying plastic material . after the plastic material is cured , the sacrificial is removed leaving a capillary channel in the sensor . the inserts may be removed by a tool including a clamp for clamping and holding each insert stationary and a sliding block to which the sensor is secured .