Hey salkan,
To use the receiver you'll need a laser that can dial in a slope percentage.
.03 % is common, 3 tenths of a foot per hundred feet. Dial that in then check the existing grade on both ends and adjust as needed.
Then like Jerry said put your cutting edge on grade and mount your laser receiver on a mast, or piece of pipe.
Here's the laser receiver on my blade. It's hooked up for automatics and an adjustable mast.
On the dozer and scraper I have a receiver with lights on it and I mount it too a 1 1/2" pipe, but don't have any pictures of that.
does the selected slope follow an uneven contour and remain the same?
So you dial the laser in, check high end and low end, adjust the dial in grade so both ends will have the same channel reading.
Now every where you check the terrace channel you want the same reading and will end up with a terrace that has no water holes.
Now the disclaimer: If your terrace turns corners it gets interesting. As long as your turn 45* or less from the direction the
laser is pointed the terrace channel will drain with no trouble. If it isn't possible to run close to the direction the laser is pointed
do a straight piece at a time, then move the level.