Abstract: A device for making skin incisions for bleeding time determinations in accordance with Ivy's method has a cutter guide on which an incising cutter is movable from a retracted position to an advanced position under the action of spring bias. A base surface adapted to be pressed against the patient's skin has a depression of a length corresponding to the desired length of the skin incision. A slot in the base surface extends across the depression and accommodates the tip of the cutter. When the cutter is released from the retracted position the spring bias displaces it along the slot and as it traverses the depression it makes a skin incision of predetermined constant depth.