You're building a wall. Besides estimating how many bricks you'll need, you also have to determine how many rows or "courses" of bricks will bring you to exactly the height you want.

You've measured from the top corners of the structure and found that you will need to build up to exactly 14 feet in height. If you just lay bricks until you get near the top, you may come out at 13.5 feet or 14.3 feet.

That's awkward, because you would have to start cutting all the bricks in the last row to make up for the difference, as the bricks themselves are over two inches thick.

All of this means that you want to plan your courses so that you can come out at 14 feet without having to cut bricks once you're at the top. It's standard practice.

During your measurement from the top corners, you make marks at every one-foot point. This is so you will be able to keep track of your progress.

Your bricks are 2.75 inches thick and you will use about one-quarter of an inch of mortar for each row, so between every one-foot marker you will expect to have laid four rows. It's an estimate, because you can't be exact with the mortar.

When you're laying your bricks and you get to one of your marks, you can see whether you are ahead (above) or behind (below) your marks. It is hard to stay right on.

Halfway up the wall, you realize that your estimate was off. Your courses are coming out ahead. At this rate, you will probably not be able to end a complete course at 14 feet. You have two options at this point.

You can go thin on the mortar and try to squeeze your work into the 14 feet. This will save a lot of time and bricks because you're already halfway done.

You can also just break the whole thing down and start over again. This will mean hours of unexpected work and more bricks, but you can refigure your estimates and make it to 14 feet more easily, without so much stretching or squeezing.

What do you do?

Keep on workingKnock it down and start over