Two tools I discovered invaluable in my latest tile job are the Bosch Tile Layout Laser and the Wagner PaintEater. The Bosch Laser built for tile and wallpaper professionals is an inexpensive tool that handles these tasks very well. I found the 45 degree lines helpful even on my jack-on-jack layout. The 45 degree lines I used to bisect my tile corners so even on tile rows already set, I could check for straightness. The 90 degree line lines up the edges of the tiles being laid and for a large room this may be the easiest way for the DIY tiler to keep his rows straight. I also used spacers even when I was relying on the laser for straightness. Check out the GTL-3 Bosch Laser.
