If you are a do-it-yourselfer, you will want to fix split or cracked boards in your floor with your own hands. As with any fixture, you should first know what tools you need. Here they are: electric drill, annular ring nails with a length that allows you to countersink them through the floorboard and almost through the sub-floor, a combination pilot bits, claw hammer, nail set, wood putty, finish that matches the floor.
You need the combination bit, or screw pilot, for making pilot holes and countersinking the fasteners. Pilot holes are excavated in floors with an electric drill before driving in screws or nails, so that the flooring is not chewed up when hammering or screwing screws. If you do not have much exercise with this device, clamp a piece of wood to a work table and practice on it.
The first step is to make pilot holes at an angle along the crack on both its sides. Then you can drive in the annular rings nails which you will countersink using the nail set. For 3/4 "floor and sub-floor, use 2" nails. The pilot bit shank should be a little shorter than the depth that the nail will be driven at. You should know that as a general rule the fastener must be larger than the pilot hole. In this way it will grab the wood surrounding the pilot hole, so it will fit tightly. When choosing the fastener, compare it to the gouges an electric device such as this can make. If the fastener fits a certain gauge, the correct hole for your drill bit is the next size smaller one.
After the nails are in, put on your snug-fitting rubber gloves and fill the nail holes and the crack with wood putty or wood filler. You can also use latex gloves. Then let the putty dry. For a good color match you can apply a color stick shellac or putty stick or finish. After it is dry you can wax or oil depending on the needs.