Turn off all power to the circular saw and remove the power cord from the wall outlet. Twist tie or tie off the cord to keep it out of the way while changing the blade,Slide up the protective blade guard to expose the blade. Lay the saw down on a sturdy bench top.,Clamp the circular saw to the bench top using two bench clamps or any clamp that will hold the unit securely to the bench. , Locate the hole in the saw blade itself. This hole will be drilled all the way through the blade and can accommodate a drill bit or another thin piece of metal or wood. Place a drill bit through the hole in the saw blade to secure the blade from moving. Many newer circular saw models come equipped with a blade lock feature that can be employed to stop blade movement .Attach a wrench or socket to the circular saw blade retaining bolt in the center of the blade. This bolt attaches the blade to the saw itself. Remove bolt and set aside. Remove the saw blade and place the new blade in its place. Replace the blade bolt and tigh