Abstract: The apparatus is for manually inserting an O-ring in a selected annular groove of a bored valve body. A valve body is placed with one end of the body's bore over a plug. A thin walled tube is placed in the other end of the bore so a gap exists between the plug and tube, adjacent the selected annular groove. Two ends of a probe are then used to urge the O-ring through the tube, passing other blocked annular grooves or air passages in the valve body, toward and into the selected annular groove. Plugs and tubes of different lengths are used to insert O-rings in annular grooves at different positions in the bore.