Tape measures have a series of lines, some longer, some shorter, that have no numbers associated with them. Many people know how to read the marked lines but not the unmarked ones. Tape measures made by different companies or for different purposes are likely to look different form one another, but they all have some things in common.
It is common for tape measures in the United States to use feet as the main increment. Typically a tape measure will display the readings for feet in large, bold print next to a heavy line indicating the exact place on the tape that it represents. To the right of the number is the letter "F," showing that the designation represents feet. This number is usually at the top of the tape, but it may be marked differently. It will still be obvious which line designates the 1-foot mark.
A foot is made up of 12 inches. On a tape measure, each inch is represented by a line that is smaller than the line used to identify a foot. Typically each inch is labelled, and every 12 inches both the inch mark and the foot mark are the same. After the first 12 inches, most tape measures continue with 13, 14, and so forth, but some tape measures also display the numbers from 1 to 12 again. The purpose of this is to make it easier to find the mark which represents a specific number such as 2 feet, 6 inches. You can find the 30-inch mark, but on tape measures that are appropriately marked you need only look for the 6-inch mark between 2 and 3 feet.
In between the inch marks are the increment marks for fractions. In the middle of the space is the half-inch mark. This will be the longest mark in the section, not including the inch marks at either end. Halfway between the inch marks and the half-inch marks are the ¼-inch lines. There will be two of these and they will both be the same length. Dividing each section in half are the 1/8-inch marks. If you were to look at a tape measure with only these increments on it, the lines on it now represent 1/8 increments from one inch to the next. Reading from 1 inch to 2 inches, the lines will represent 1 inch, 1 1/8 inches, 1 2/8 inches (same as 1 ¼), 1 3/8 inches, 1 4/8 inches (same as 1 ½), 1 5/8 inches, 1 6/8 inches (same as 1 ¾), 1 7/8 inches, and 2 inches. Most measuring tapes are further divided into 1/16 inch increments and 1/32 increments. These serve to allow measuring to be more precise and work exactly the same way as the other incremental marks.