Are you trying to remove the pedal crank arm? If so, you are trying to get the pin out that holds the arm to the shaft. Remove the nut and washer and then do one of two things. If you had done this before on a bicycle you will know how to hit the threaded end while supporting the shaft with a 2x4. It takes a sharp blow which only by experience will you get the correct technique. Continued pounding will not do it nor will a sledge, use a 1-1/2 lb claw hammer with a flat face. The other way is to rig some sort of setup using a gear puller to press the pin out. Plan to replace the pin, washer and nut, they are available at bike shops. Good luck.