laserThis floor set-out laser draws two red lines on the floor or any other surface it is placed on. These two lines intersect at 90 deg (right Angle) about 1" (25mm) from the pointy end of the unit. There are several of these on the market ,this one retails about $200 dollars or so. Now if you are an old codger like me you would have learnt how to do this with a 3 foot rule and a chalk line. This was done following Mr.Pythagros theory of 3.4.5. which makes an mathematical right angle (90deg). A real bitch to do by yourself in 3mt, 4mt, 5mt increments! (not to mention holding and flicking the chalk line by yourself - very handy, that 6" length of heavy train line). This would be one of the tilers most used tools. Can not be used in direct sunlight. NB: Can be used as a wall level as well. Draw a vertical line on the wall with a stick level, then place one of the red lines over it. This means that the other line is level!