Changing the blade on a Craftsman utility knife is very easy. First, you must remove the old blade by pressing down on the end of the knife to release it from its housing. Next, slide out the old blade and discard it in a safe place away from children's reach. Then, select a new replacement blade that fits your particular model of utility knife (these can be found at hardware stores or online). Once you have chosen an appropriate size and type of replacement blade for your Craftsman utility knife, insert it into the handle and make sure that all edges of the new blade are properly aligned with each other. Finally, press down firmly on both ends of the handle to secure it in place before using your newly sharpened tool!