Caulk is a waterproof joint filler used to finish off the edges of floor tiles installations, and help make transitions between two surfaces like a marble tile wall and a bathtub. Most caulks come in color and texture similar to the grout used with the rest of the floor tiles; when applied properly the caulk will blend right into the rest of the installation.

Wipe down the edges of the ceramic tiles with a clean cloth. Remove any dust, debris or construction materials that may prevent the caulk from forming a good seal around the tiles. If the design tiles or surrounding area is wet, allow it to dry completely.

Cut the tip of the caulk tube off at a 45 degree angle. Make this cut only as large as the grout joints that surround the polished porcelain tiles; this will provide the right amount of caulk for the space.

Insert the tip of the caulk tube into the caulking gun. Push in the plunger on the back of the caulking gun and tighten down the gun so minimal pressure will release the caulk. Start at the top right of the installation and work down and to the left.

Squeeze a thin bead of caulk in a continuous line around the wood tiles to be caulked. Try to keep the caulk in the center of the joint. Wet your index finger and use it to smooth the caulk into place in the joint. Lightly press down on the caulk and drag your finger along the edges of the floor tiles. Let the caulk dry for 24 hours before using the wall tiles space again.