A cheese slicer has a simple construction, consisting of a wire held taunt between the arms of a Y-shaped handle. Over time, this wire can wear or break, which requires a replacement. Replacement cheese wire is sold whereever cooking utensils are sold. Measure the distance between the arms of the cheese slicer to know the size of replacement wire to buy. If you cannot find cheese wire, Alton Brown recommends using a guitar string to cut the cheese.
Loosen and remove the screw at the end of one of the arms holding the wire in place in the slot at the end of the arm.
Pry out the end of the old wire from that arm with the tip of a nail.
Repeat the process on the opposite arm to completely remove the old wire.
Loop the ends of the new wire into the slots for the wire on the arms.
Replace and tighten the holding screws.