Abstract: A drill instrument with calibrated depressions as markings on the shaft set at determinable distances apart, e.g. at 1 mm increments is disclosed. These calibrations are designed to give a visible depth gauge indication when the tip or point of the drill is at the full length of the depth of a drilled hole. A stop means is variably fixable to the drill at determinable locations. This stop defines a predetermined length available for drilling a hole into bone or a tooth canal up to the precise location of the stop on the drill corresponding to the depth desired to be drilled.An organizer block or kit accommodates the drills and stops of the invention and preferably provides an alignment device for preparing drills having the pre-determined lengths according to the invention via a drill-length determining device for applying the stop means to the drill at the desired pre-determined length.