Cut the high quality wood down to a block about 2-inches square.
Cut the strip of ebony down to the same dimensions as the block of wood.
Glue the ebony piece to the top of the wood and clamp it for several days, giving it time to adequately set.
Using a saw, cut a quarter-inch off from the glued wood. The resulting template should be one-quarter-inch wide and 1-inch high and 2-inches long. The strip of ebony should span top of the length of the strip.
Mark the top (ebony side up) at 1.5 centimeters, 4.5 centimeters and 7.5 centimeters. This will give you the end of the wings and the center.
Draw a line across the strip five-eighths of an inch down from the top.
Draw a line from the 4.5 centimeter center mark straight down through the five-eighths inch line across the strip.
Drill a hole where the two lines intersect.
Use a saw to cut along the five-eighths-inch line, directly through the drilled hole.
Use a belt sander or files and sandpaper to carve a semi-circle from the drill hole in the bottom to the edge. Be sure sure to leave about a quarter-inch on the edges of the semicircle to the edge of the drill hole and the strip edge.
Sand the other side of the drill hole to match the opposite side.
Sand down the corners of the top of the strip from the 1.5 centimeter and 7.5 centimeter marks to the center of the shorter outside edges. This will give the final sanded bridge the look of two wings and three contact points with the banjo.
Measure out the slots for the strings. For a five-string banjo it's every 1.2 centimeters and for a four-string banjo, it's every 1.5 centimeters.
Taking a file very softly file off each mark. The side of the bridge facing the neck of the banjo should have a very shallow groove. The rear of the slot should be deeper, allowing the strings to angle toward the bottom.
Mark the front of the bridge so that it is properly put onto the banjo.