Remove the bolt or screw holding the safety housing in the slide. Push the safety housing up and out of the way to get to the bolt in the center of the blade. Attach firmly a vice grips pliers to any place on the blade. Turn the center bolt out and the pliers will turn also until they run into the housing. This will then make turning the blade bolt out quite easy. Many of these type saws do have locking mechanisms but you don't have to use them if you have a vice grips pliers.