Wood-burning stoves use fire brick to insulate and distribute heat evenly. The floor and the interior walls of stoves are completely lined with these special bricks. Occasionally the bricks crack or break, will not stay in place and need to be replaced. Most fire bricks are the same size and can be found in most home improvement stores. They are easy to replace.
Purchase a standard firebrick.
Clean the ashes out of the stove. Find the broken brick.
Grab the firebrick with your fingers and try to pull it out. If it won't budge, use the tip of a screwdriver to pry it up and then grab it. Take out any residual pieces as well and discard them.
Use a small brush to brush out any ashes from the recessed area where the brick came out.
Place the new firebrick into place with your fingers. If it will not fit, gently tap on it with a small block of wood until it fits flush.
Lay a dust sheet in front of your stove when removing the ashes. If the firebrick is on the side, or vertically stacked, they are held in place by gravity. These bricks can be rearranged. Just let the remaining bricks fall into place where the damaged brick came out, and place the new brick on top.
Don't tap on the brick with a hammer. It might break the brick.