A see-through plastic ruler with eighth inch grid markings is a must for the serious sewer. These rulers allow you to lay the ruler over the edge and see what you are marking. The grid marks help to keep things aligned straight while marking.
A seam gauge is a six inch ruler with a sliding marker to keep track of the exact measurement you are using. This small gauge is a quick and accurate measuring device. Most seam gauges are made out of a thin metal so they are easy to bend out of shape.
For accuracy, replace when it gets bent or the sliding marker gets loose.
It is important to have a yardstick or longer ruler. This measuring tool is necessary for longer measuring tasks, such as measuring from the floor to the hemline and extending a grain line.