Asking a student to cut a piece of wood exactly in half will require a fraction. At least one. Remember? It's the kerf from the saw. Kerf defined is the part of the wood that turns into saw dust. Depending on the saw, it could be anywhere from a 16th of an inch up to 3/16ths of an inch.

First we need to teach the basic use of the tape measure. I draw an enlarged view on the board. A huge inch. It includes each little line within the inch. Some small, some big. Take a close look at your tape measure. The biggest lines are for the full inch. The next longest line is for the 1/2", then 1/4", the 1/8th and finally 1/16". having this on the board will assist the students. They should also have this written down. Letting the student employ the smallest set of lines, and simply counting how many 16ths are involved in the measurement, will simplify their project.