Mark a horizontal line across the wall, from end to end, using a level and pencil, at the height you want the chair rail. Standard chair rails are 32 to 46 inches up from the floor.
Measure the length of the line. Mark the halfway point.
Spread tile adhesive on the back of a trim tile with a notched trowel, covering the tile completely. Press it to the wall, under the horizontal line and on one side of the center mark.
Cover the second tile with adhesive and press it next to the first, under the line. Put spacers between the tiles.
Repeat and continue, hanging the rest of the tiles along the border, building out in both directions and forming the rail. Put spacers between all of them. Cut the end tiles on a tile cutter as necessary.
Let the adhesive set for 10 hours. Pull out the spacers.
Spread grout over the tiles, using a grout float. Press the grout into the spaces between the tiles while scraping it off the surface. Use a damp sponge to wipe off excess grout.